diff --git a/fastNLP/core/drivers/torch_driver/single_device.py b/fastNLP/core/drivers/torch_driver/single_device.py
index 034292eb..952712be 100644
--- a/fastNLP/core/drivers/torch_driver/single_device.py
+++ b/fastNLP/core/drivers/torch_driver/single_device.py
@@ -130,8 +130,8 @@ class TorchSingleDriver(TorchDriver):
         else:
             return self._test_step(batch)
 
-    def set_dist_repro_dataloader(self, dataloader, dist: Union[str, ReproducibleBatchSampler, ReproducibleIterator],
-                                  reproducible: bool = False, sampler_or_batch_sampler=None):
+    def set_dist_repro_dataloader(self, dataloader, dist: Union[str, ReproducibleBatchSampler, ReproducibleIterator]=None,
+                                  reproducible: bool = False):
         if isinstance(dist, ReproducibleBatchSampler):
             return replace_batch_sampler(dataloader, dist)
         elif isinstance(dist, ReproducibleIterator):
diff --git a/fastNLP/core/samplers/__init__.py b/fastNLP/core/samplers/__init__.py
index f0e55062..68928b66 100644
--- a/fastNLP/core/samplers/__init__.py
+++ b/fastNLP/core/samplers/__init__.py
@@ -11,11 +11,11 @@ __all__ = [
     'PollingSampler',
     'ReproducibleIterator',
     'RandomSampler',
-    'ReproducibleBatchSampler',
     're_instantiate_sampler'
 ]
 
 from .sampler import BucketSampler, SortedSampler, ConstTokenNumSampler, ConstantTokenNumSampler, UnrepeatedDistributedSampler
 from .mix_sampler import MixSampler, InnerSampler, DopedSampler, MixSequentialSampler, PollingSampler
-from .reproducible_sampler import ReproducibleIterator, RandomSampler, ReproducibleBatchSampler, re_instantiate_sampler
+from .reproducible_sampler import ReproducibleIterator, RandomSampler, re_instantiate_sampler
+from .reproducible_batch_sampler import ReproducibleBatchSampler, BucketedBatchSampler
 
diff --git a/fastNLP/core/samplers/reproducible_batch_sampler.py b/fastNLP/core/samplers/reproducible_batch_sampler.py
new file mode 100644
index 00000000..3e39aca5
--- /dev/null
+++ b/fastNLP/core/samplers/reproducible_batch_sampler.py
@@ -0,0 +1,397 @@
+__all__ = [
+    'BucketedBatchSampler',
+    "ReproducibleBatchSampler"
+]
+
+import math
+from array import array
+from copy import deepcopy
+from typing import Dict, Union, List
+from itertools import chain
+
+import numpy as np
+
+from fastNLP.core.dataset import DataSet
+from fastNLP.core.log import logger
+from abc import abstractmethod
+
+
+class ReproducibleBatchIterator:
+    @abstractmethod
+    def set_distributed(self, num_replicas, rank, pad=True):
+        raise NotImplementedError("Each specific batch_sampler should implement its own `set_distributed` method.")
+
+    @abstractmethod
+    def __len__(self):
+        raise NotImplementedError("Each specific batch_sampler should implement its own `__len__` method.")
+
+    @abstractmethod
+    def __iter__(self):
+        raise NotImplementedError("Each specific batch_sampler should implement its own `__iter__` method.")
+
+    @abstractmethod
+    def state_dict(self):
+        raise NotImplementedError("Each specific batch_sampler should implement its own `state_dict` method.")
+
+    @abstractmethod
+    def load_state_dict(self, states):
+        raise NotImplementedError("Each specific batch_sampler should implement its own `load_state_dict` method.")
+
+    @abstractmethod
+    def set_epoch(self, epoch):
+        pass
+
+
+class ReproducibleBatchSampler(ReproducibleBatchIterator):
+    # 这两个参数的值应当交给 driver 的 get_dataloader_args 函数去拿；
+    def __init__(self, batch_sampler, batch_size: int, drop_last: bool, **kwargs):
+        """
+        可以使得 batch_sampler 对象状态恢复的 wrapper 。
+
+        :param batch_sampler: 可迭代出 数字 或 数字列表 的可迭代对象。ReproducibleBatchSampler 将首先遍历一边该对象，然后将迭代
+            出来的序号暂存起来，使用时按照 batch_size 的 batch 大小吐出序号列表。
+        :param batch_size: 每个 batch 的大小是多少。
+        :param drop_last: 如果最后一个 batch 无法构成 batch_size 那么多个 sample ，是否丢掉。
+        :param kwargs: fastNLP 内部使用。
+        """
+        self.batch_sampler = batch_sampler
+        self.batch_size = batch_size
+        self.drop_last = drop_last
+
+        self.data_idx = kwargs.get("data_idx", 0)
+
+        self.index_list = kwargs.get("index_list", self._iterate_sampler())
+        self.need_reinitialize = kwargs.get("need_reinitialize", False)
+
+    def _iterate_sampler(self):
+        _index_lst = []
+        for idx in self.batch_sampler:
+            if isinstance(idx, list):
+                _index_lst.extend(idx)
+            # 说明是在初始化时传入的是一个 sampler，理论上对应于 dataloader 在初始化时没有 batch_size，也没有 batch_sampler 的情况；
+            else:
+                _index_lst.append(idx)
+        # 64 位机器的 unsigned int 为 4 个字节，能表示的最大大小为 4294967295；
+        if len(_index_lst) > 4294967295:
+            # 注意 self.index_list 内存放的是全部数据的 index；
+            # unsigned long
+            _index_lst = array("L", _index_lst)
+        else:
+            # unsigned int
+            _index_lst = array("I", _index_lst)
+        return _index_lst
+
+    def __iter__(self):
+        if self.need_reinitialize:
+            self.index_list = self._iterate_sampler()
+            self.data_idx = 0
+        else:
+            self.need_reinitialize = True
+
+        batch = []
+        if self.data_idx:
+            index_list = self.index_list[self.data_idx:]
+        else:
+            index_list = self.index_list
+        for idx in index_list:
+            batch.append(idx)
+            self.data_idx += 1
+            if len(batch) == self.batch_size:
+                yield batch
+                batch = []
+        if len(batch) > 0 and not self.drop_last:
+            yield batch
+
+    def __len__(self) -> int:
+        if self.drop_last:
+            return len(self.index_list) // self.batch_size
+        else:
+            return (len(self.index_list) + self.batch_size - 1) // self.batch_size
+
+    def state_dict(self) -> Dict:
+        return {"index_list": deepcopy(self.index_list), "data_idx": self.data_idx, 'sampler_type': self.__class__.__name__}
+
+    def load_state_dict(self, states: Dict):
+        assert states['sampler_type'] == self.__class__.__name__, f"The sampler type in checkpoint is {states['sampler_type']}," \
+                                                               f"we cannot use {self.__class__.__name__} to load it."
+
+        _index_list = states["index_list"]
+        assert len(_index_list) == len(self.index_list), "The number of samples is different between the checkpoint " \
+                                                          "record and current dataset."
+        self.index_list = _index_list
+        self.data_idx = states["data_idx"]
+        self.need_reinitialize = False
+
+    def set_distributed(self, num_replicas, rank, pad=True):
+        raise RuntimeError(f"ReproduceBatchSampler does not support to change to distributed training.")
+
+    def set_epoch(self, epoch):
+        if hasattr(self.batch_sampler, "sampler") and hasattr(self.batch_sampler.sampler, 'set_epoch') and callable(self.batch_sampler.sampler.set_epoch):
+            self.batch_sampler.sampler.set_epoch(epoch)
+
+    @property
+    def batch_idx_in_epoch(self):
+        if self.drop_last:
+            return len(self.index_list) // self.batch_size - (len(self.index_list) - self.data_idx) // self.batch_size
+        else:
+            return (len(self.index_list) + self.batch_size - 1) // self.batch_size - \
+                   (len(self.index_list) - self.data_idx + self.batch_size - 1) // self.batch_size
+
+
+class BucketedBatchSampler(ReproducibleBatchIterator):
+    def __init__(self, dataset, length: Union[List[int], str], batch_size:int = 32, num_batch_per_bucket:int = 10,
+                 shuffle: bool = True, drop_last: bool = False, seed: int = 0, **kwargs):
+        """
+        首先按照 sample 的长度排序，然后按照 batch_size*num_batch_per_bucket 为一个桶的大小，sample 只会在这个桶内进行组合，这样
+            每个 batch 中的 padding 数量会比较少 （因为桶内的数据的长度都接近）。
+
+        :param dataset: 实现了 __len__ 方法的数据容器。
+        :param length: 如果为 List，应当与 dataset 有一样的长度，表示 dataset 中每个元素的数量；仅当传入的 dataset 为 fastNLP 的
+            DataSet 时支持传入 str，会将该str理解为 dataset 的 field 名称，若 field 中的元素为 int，则认为该值是 sample 的长度。
+            如果否则使用 len() 函数得到每个 sample 中这个 field 的长度。
+        :param batch_size: 每个 batch 的大小
+        :param num_batch_per_bucket: 多少个 batch 组成一个桶，数据只会在一个桶内进行 shuffle 。
+        :param shuffle: 如果为 True，将不进行 shuffle，实际上数据会以从长到短的方式输出。
+        :param drop_last: 如果最后一个 batch 的 sample 数量无法凑齐 batch_size 这么多，是否需要丢掉。
+        :param seed: 设置的随机数种子
+        :param kwargs: fastNLP 保留使用
+        """
+        super().__init__()
+        if isinstance(dataset, DataSet):
+            length = dataset.get_field(length)
+            if not isinstance(length[0], int):
+                length = list(map(len, length))
+        else:
+            assert len(length) == len(dataset), "When the dataset is not fastNLP.DataSet, " \
+                                              "the length parameter can only be List[int]"
+
+        assert len(length) == len(dataset), "The length of `data` and `length` should be equal."
+
+        self.dataset = dataset
+        self.length = np.array(length, dtype=int)  # 按照长到短排列的序号。
+        self.sorted_indices = np.argsort(self.length)[::-1]  # 按长度从高到低排序的
+
+
+        self.batch_size = batch_size
+        self.num_batch_per_bucket = num_batch_per_bucket
+        self.shuffle = shuffle
+        self.drop_last = drop_last
+        self.seed = seed
+
+        self.num_consumed_samples = kwargs.get("num_consumed_samples", 0)  # 总共迭代了多少数据了，包括多卡情况下的其它卡上的输出的数量
+
+        # 多卡的相关的参数
+        self.num_replicas = kwargs.get("num_replicas", 1)
+        self.rank = kwargs.get("rank", 0)
+        self.epoch = kwargs.get("epoch", -1)
+        self.pad = kwargs.get("pad", False)  # 该参数在单卡上不具有任何意义；
+
+        # 是否处于iteration之间，为True不允许调用 set_distributed()和load_state_dict()
+        self.during_iter = kwargs.get("during_iter", False)
+
+        # 以下变量为内部使用恢复状态的变量。
+        self.old_batch_size = kwargs.get('old_batch_size', self.batch_size)
+        self.old_num_batch_per_bucket = kwargs.get('old_num_batch_per_bucket', self.num_batch_per_bucket)
+
+    def set_distributed(self, num_replicas, rank, pad=True):
+        assert self.during_iter is False, "Cannot set the sampler to be distributed when it is " \
+                                           "during an unfinished iteration."
+        assert num_replicas > 0 and isinstance(num_replicas, int)
+        assert isinstance(rank, int) and 0 <= rank < num_replicas
+        # 注意初始化该函数时，所有的状态都应当默认是一个 epoch 刚开始训练的状态；
+        self.num_replicas = num_replicas
+        self.rank = rank
+        self.pad = pad
+
+        num_samples = (len(self.dataset)+self.num_replicas-1)//self.num_replicas*self.num_replicas if pad \
+            else len(self.dataset)
+
+        if self.drop_last:
+            assert self.num_replicas*self.batch_size<=num_samples, "The number of samples should be greater " \
+                                                                    "than the number of replicates multiplied " \
+                                                                    "with batch_size when drop_last=True."
+
+        return self
+
+    @property
+    def total_size(self):
+        """
+        这个变量代表的含义是当前这个sampler会最终产生出的index数量（包括了其它rank的），因为replica和pad的原因，这个值可能等于、
+            大于或者小于len(dataset)
+
+        :return:
+        """
+        return self.num_consumed_samples + self.num_replicas*self.num_left_samples
+
+    @property
+    def num_left_samples(self):
+        """
+        返回当前 iteration 还有多少个 sample 结束，表示的是当前 rank 的还剩多少。
+
+        :return:
+        """
+        num_consumed_samples = self.num_consumed_samples
+        return math.ceil((len(self.dataset) - num_consumed_samples) / self.num_replicas) if \
+            self.pad else math.floor(((len(self.dataset) - num_consumed_samples) / self.num_replicas))
+
+    def __len__(self):
+        """
+        返回当前 sampler 还会返回多少个 batch 的数据
+
+        :return:
+        """
+        num_sampler_per_rank = self.total_size//self.num_replicas
+        num_batches = num_sampler_per_rank//self.batch_size if self.drop_last else \
+            (num_sampler_per_rank+self.batch_size-1)//self.batch_size
+        return num_batches
+
+    def __iter__(self):
+        if self.during_iter:  # 如果发现_during_iter为True，说明之前的还没结束，只有强制重新初始化了
+            self.num_consumed_samples = 0
+        self.during_iter = True
+
+        sorted_indices = deepcopy(self.sorted_indices).tolist()  # 按长度从高到低排序的
+
+        if self.shuffle:
+            if self.num_consumed_samples > 0:  # 需要先按照原来的排序，删掉多余的
+                _batches = []
+                for _i in range(self.old_num_replicas):
+                    _sorted_indices = sorted_indices[_i:len(sorted_indices):self.old_num_replicas]
+                    __batches = self.bucketerize(_sorted_indices, self.old_batch_size, self.old_num_batch_per_bucket,
+                                               seed=self.seed+self.epoch)
+                    _batches.append(__batches)
+                batches = list(chain(*[_ for _ in zip(*_batches)]))
+                sorted_indices = list(chain(*batches))
+                sorted_indices = sorted_indices[self.num_consumed_samples:]
+                # 再进行排序
+                sub_length = self.length[sorted_indices]
+                sorted_indices = np.array(sorted_indices)[np.argsort(sub_length)[::-1]]  # 按长度从高到低排序的
+            # 取出这个 rank ，
+            sorted_indices = sorted_indices[self.rank:len(sorted_indices):self.num_replicas]
+            batches = self.bucketerize(sorted_indices, self.batch_size, self.num_batch_per_bucket,
+                                       seed=self.seed+self.epoch)
+            batches = list(map(list, batches))
+        else:
+            sorted_indices = sorted_indices[self.num_consumed_samples:]
+            sorted_indices = sorted_indices[self.rank:len(sorted_indices):self.num_replicas]
+            _num_batches = len(sorted_indices) // self.batch_size
+            if _num_batches == 0:
+                batches = [sorted_indices]
+            else:
+                batches = list(map(list, np.array_split(sorted_indices[:_num_batches*self.batch_size], _num_batches)))
+                if len(sorted_indices)%self.batch_size!=0:
+                    batches.append(sorted_indices[_num_batches*self.batch_size:])
+
+        need_pad_num = (len(self.dataset)-self.num_consumed_samples) % self.num_replicas
+        if self.pad and need_pad_num !=0 and need_pad_num<=self.rank:
+            if len(batches) > 0:
+                if len(batches[-1])<self.batch_size:
+                    batches[-1].append(batches[-1][0])  # 这里可以保证这个bucket的长度没被破坏。
+                else:
+                    batches.append([batches[-1][0]])
+        elif self.pad is False and need_pad_num !=0 and need_pad_num>self.rank:
+            if len(batches):
+                batches[-1].pop(-1)
+            if len(batches[-1])==0:
+                batches.pop(-1)
+
+        assert len(list(chain(*batches))) == self.num_left_samples
+
+        if self.drop_last and len(batches) >= 1 and len(batches[-1]) < self.batch_size:
+            batches = batches[:-1]
+
+        for batch in batches:
+            self.num_consumed_samples += self.num_replicas * len(batch)
+            yield list(map(int, batch))
+        self.during_iter = False
+        self.num_consumed_samples = 0
+        self.old_batch_size = self.batch_size
+        self.old_num_batch_per_bucket = self.num_batch_per_bucket
+        self.old_num_replicas = self.num_replicas
+        if self.epoch < 0:  # 防止用户没有修改epoch，导致每个epoch都一样了
+            self.epoch -= 1
+
+    def bucketerize(self, sorted_indices, batch_size, num_batch_per_bucket, seed):
+        """
+        将 indices 分桶
+
+        :param sorted_indices: List[int]
+        :param batch_size: int
+        :param num_batch_per_bucket: int
+        :param seed: int
+        :return:  List[List[int]]
+        """
+        # 实际的 bucket 大小
+        bucket_size = min(len(sorted_indices), batch_size * num_batch_per_bucket)
+        rng = np.random.default_rng(abs(seed))
+        num_buckets = (len(sorted_indices) + bucket_size - 1) // bucket_size
+        batches = []
+        batch_indices = []
+        for i in range(num_buckets):
+            bucket = sorted_indices[i * bucket_size:(i + 1) * bucket_size]
+            rng.shuffle(bucket)  # bucket 内部 shuffle 一下
+            _num_batches = len(bucket) // batch_size
+            if _num_batches == 0:
+                _batches = [bucket]
+            else:
+                _batches = np.array_split(bucket[:_num_batches*batch_size], _num_batches)
+                if len(bucket) % batch_size != 0:
+                    _batches.append(bucket[_num_batches*batch_size:])
+            batch_indices.extend(list(range(len(batches), len(batches) + len(_batches))))
+            batches.extend(_batches)
+        last_batches = []
+        # 最后一个batch 统一不参与shuffle，因为有的rank最后一个 batch 可能不足一个batch_size （不足的时候
+        #  一定要放在末尾，所以就干脆所有的rank都不对最后一个batch进行shuffle）。
+        if len(batches) >= 1:
+            last_batches = [list(batches[-1])]
+        batch_indices = list(batch_indices[:-1])
+        rng = np.random.default_rng(abs(seed))  # 这里防止由于bucket长度不同，对随机数状态有影响
+        rng.shuffle(batch_indices)  # 不同的 batch 也 shuffle ，当前这种可以保证每张卡上每个 batch 长度都接近的。
+        batches = (np.array(batches)[batch_indices]).tolist()
+        if last_batches:
+            batches = batches + last_batches
+        return batches
+
+    def state_dict(self) -> Dict:
+        if self.old_batch_size != self.batch_size or self.old_num_batch_per_bucket != self.num_batch_per_bucket:
+            raise RuntimeError("BucketedBatchSampler does not support saving before last checkpoint states have been"
+                               " consumed. ")
+        states = {
+            'seed': self.seed,
+            'epoch': self.epoch,
+            'num_consumed_samples': self.num_consumed_samples,  # 注意该值是计算所有 rank 上训练的所有数据；
+            'sampler_type': self.__class__.__name__,
+            'length': len(self.dataset),
+            'shuffle': self.shuffle,
+            'batch_size': self.batch_size,
+            'num_batch_per_bucket': self.num_batch_per_bucket,
+            'num_replicas': self.num_replicas
+        }
+        return states
+
+    def load_state_dict(self, states: Dict):
+        # 如果 self.during_iter 是 True，那么 data_idx 一定是 0；
+        assert self.during_iter is False, "Cannot call load_state_dict() when it is " \
+                                          "during an unfinished iteration."
+
+        assert states['sampler_type'] == self.__class__.__name__, f"The sampler type in checkpoint is {states['sampler_type']}," \
+                                                                  f"we cannot use {self.__class__.__name__} to load it."
+
+        length = states['length']
+        assert length == len(self.dataset), "The number of samples is different between the checkpoint record " \
+                                            "and current dataset."
+        self.seed = states['seed']
+        self.epoch = states['epoch']
+        self.num_consumed_samples = states['num_consumed_samples']
+        if self.num_consumed_samples>=length:  # 如果保存的时候已经到达了最后一个sample了，则直接将结果重置为0
+            self.num_consumed_samples = 0
+        if self.shuffle != states['shuffle']:
+            logger.info(f"The shuffle from the checkpoint is {states['shuffle']}, while set as {self.shuffle}, "
+                        f"we use shuffle={states['shuffle']}")
+        self.shuffle = states["shuffle"]
+        self.old_batch_size = states['batch_size']
+        self.old_num_batch_per_bucket = states['num_batch_per_bucket']
+        self.old_num_replicas = states['num_replicas']
+
+    def set_epoch(self, epoch):
+        self.epoch = epoch
\ No newline at end of file
diff --git a/fastNLP/core/samplers/reproducible_sampler.py b/fastNLP/core/samplers/reproducible_sampler.py
index 1382282a..0a4ac7bf 100644
--- a/fastNLP/core/samplers/reproducible_sampler.py
+++ b/fastNLP/core/samplers/reproducible_sampler.py
@@ -1,14 +1,12 @@
 from typing import Dict, List
 import math
 import numpy as np
-from array import array
-from copy import deepcopy
 
+from fastNLP.core.log import logger
 
 __all__ = [
     'ReproducibleIterator',
     'RandomSampler',
-    'ReproducibleBatchSampler',
     're_instantiate_sampler'
 ]
 
@@ -22,7 +20,8 @@ def re_instantiate_sampler(sampler):
 class ReproducibleIterator:
     """
     注意所有继承 `ReproducibleIterator` 的类的  `__init__` 方法中都需要加入参数 `**kwargs`，用来使我们再断点重训时重新实例化这个 sampler
-     或者 batch_sampler；
+     或者 batch_sampler；注意，所有在 init 中初始化的变量，都不能含有 _ 下横线作为开头；所有不在 init 中设置的变量都必须以下横线开头。
+
     """
 
     def set_distributed(self, num_replicas, rank, pad=True):
@@ -72,7 +71,7 @@ class RandomSampler(ReproducibleIterator):
         self.pad = kwargs.get("pad", False)  # 该参数在单卡上不具有任何意义；
 
         # 是否处于iteration之间，为True不允许调用 set_distributed()和load_state_dict()
-        self._during_iter = kwargs.get("_during_iter", False)
+        self.during_iter = kwargs.get("during_iter", False)
 
     def __len__(self):
         """
@@ -92,9 +91,9 @@ class RandomSampler(ReproducibleIterator):
             >>> next(iter2)  # 当前num_consumed_samples的数量会发生变化
         """
 
-        if self._during_iter:  # 如果发现_during_iter为True，说明之前的还没结束，只有强制重新初始化了
+        if self.during_iter:  # 如果发现_during_iter为True，说明之前的还没结束，只有强制重新初始化了
             self.num_consumed_samples = 0
-        self._during_iter = True
+        self.during_iter = True
         indices = self.generate_indices()
 
         if self.pad:
@@ -118,7 +117,7 @@ class RandomSampler(ReproducibleIterator):
         for index in indices:
             self.num_consumed_samples += self.num_replicas
             yield index
-        self._during_iter = False
+        self.during_iter = False
         self.num_consumed_samples = 0
 
     def generate_indices(self) -> List[int]:
@@ -150,8 +149,8 @@ class RandomSampler(ReproducibleIterator):
         return states
 
     def load_state_dict(self, states: Dict):
-        # 如果 self._during_iter 是 True，那么 data_idx 一定是 0；
-        assert self._during_iter is False, "Cannot call load_state_dict() when it is " \
+        # 如果 self.during_iter 是 True，那么 data_idx 一定是 0；
+        assert self.during_iter is False, "Cannot call load_state_dict() when it is " \
                                            "during an unfinished iteration."
 
         assert states['sampler_type'] == self.__class__.__name__, f"The sampler type in checkpoint is {states['sampler_type']}," \
@@ -165,6 +164,9 @@ class RandomSampler(ReproducibleIterator):
         self.num_consumed_samples = states['num_consumed_samples']
         if self.num_consumed_samples>=length:  # 如果保存的时候已经到达了最后一个sample了，则直接将结果重置为0
             self.num_consumed_samples = 0
+        if self.shuffle != states['shuffle']:
+            logger.info(f"The shuffle from the checkpoint is {states['shuffle']}, while set as {self.shuffle}, "
+                        f"we use shuffle={states['shuffle']}")
         self.shuffle = states["shuffle"]
 
     def set_epoch(self, epoch: int) -> None:
@@ -181,7 +183,7 @@ class RandomSampler(ReproducibleIterator):
         :return:
         """
 
-        assert self._during_iter is False, "Cannot set the sampler to be distributed when it is " \
+        assert self.during_iter is False, "Cannot set the sampler to be distributed when it is " \
                                            "during an unfinished iteration."
         assert num_replicas>0 and isinstance(num_replicas, int)
         assert isinstance(rank, int) and 0<=rank<num_replicas
@@ -204,7 +206,7 @@ class RandomSampler(ReproducibleIterator):
     @property
     def num_left_samples(self):
         """
-        返回当前 iteration 还有多少个 sample 结束
+        返回当前 iteration 还有多少个 sample 结束。表示的是当前 rank 的还剩多少
 
         :return:
         """
@@ -213,119 +215,8 @@ class RandomSampler(ReproducibleIterator):
             self.pad else math.floor(((len(self.dataset) - num_consumed_samples) / self.num_replicas))
 
 
-class ReproducibleBatchSampler:
-    # 这两个参数的值应当交给 driver 的 get_dataloader_args 函数去拿；
-    def __init__(self, batch_sampler, batch_size: int, drop_last: bool, **kwargs):
-        """
-        可以使得 batch_sampler 对象状态恢复的 wrapper 。
-
-        :param batch_sampler: 可迭代出 数字 或 数字列表 的可迭代对象。ReproducibleBatchSampler 将首先遍历一边该对象，然后将迭代
-            出来的序号暂存起来，使用时按照 batch_size 的 batch 大小吐出序号列表。
-        :param batch_size: 每个 batch 的大小是多少。
-        :param drop_last: 如果最后一个 batch 无法构成 batch_size 那么多个 sample ，是否丢掉。
-        :param kwargs: fastNLP 内部使用。
-        """
-        self.batch_sampler = batch_sampler
-        self.batch_size = batch_size
-        self.drop_last = drop_last
-
-        self.data_idx = kwargs.get("data_idx", 0)
-
-        self._index_list = kwargs.get("_index_list", self._iterate_sampler())
-        self.need_reinitialize = kwargs.get("need_reinitialize", False)
-
-    def _iterate_sampler(self):
-        _index_lst = []
-        for idx in self.batch_sampler:
-            if isinstance(idx, list):
-                _index_lst.extend(idx)
-            # 说明是在初始化时传入的是一个 sampler，理论上对应于 dataloader 在初始化时没有 batch_size，也没有 batch_sampler 的情况；
-            else:
-                _index_lst.append(idx)
-        # 64 位机器的 unsigned int 为 4 个字节，能表示的最大大小为 4294967295；
-        if len(_index_lst) > 4294967295:
-            # 注意 self._index_list 内存放的是全部数据的 index；
-            # unsigned long
-            _index_lst = array("L", _index_lst)
-        else:
-            # unsigned int
-            _index_lst = array("I", _index_lst)
-        return _index_lst
-
-    def __iter__(self):
-        if self.need_reinitialize:
-            self._index_list = self._iterate_sampler()
-            self.data_idx = 0
-        else:
-            self.need_reinitialize = True
-
-        batch = []
-        if self.data_idx:
-            index_list = self._index_list[self.data_idx:]
-        else:
-            index_list = self._index_list
-        for idx in index_list:
-            batch.append(idx)
-            self.data_idx += 1
-            if len(batch) == self.batch_size:
-                yield batch
-                batch = []
-        if len(batch) > 0 and not self.drop_last:
-            yield batch
-
-    def __len__(self) -> int:
-        if self.drop_last:
-            return len(self._index_list) // self.batch_size
-        else:
-            return (len(self._index_list) + self.batch_size - 1) // self.batch_size
-
-    def state_dict(self) -> Dict:
-        return {"index_list": deepcopy(self._index_list), "data_idx": self.data_idx, 'sampler_type': self.__class__.__name__}
-
-    def load_state_dict(self, states: Dict):
-        assert states['sampler_type'] == self.__class__.__name__, f"The sampler type in checkpoint is {states['sampler_type']}," \
-                                                               f"we cannot use {self.__class__.__name__} to load it."
-
-        _index_list = states["index_list"]
-        assert len(_index_list) == len(self._index_list), "The number of samples is different between the checkpoint " \
-                                                          "record and current dataset."
-        self._index_list = _index_list
-        self.data_idx = states["data_idx"]
-        self.need_reinitialize = False
-
-    def set_distributed(self):
-        raise RuntimeError(f"ReproduceBatchSampler does not support to change to distributed training.")
-
-    def set_epoch(self, epoch):
-        if hasattr(self.batch_sampler, "sampler") and hasattr(self.batch_sampler.sampler, 'set_epoch') and callable(self.batch_sampler.sampler.set_epoch):
-            self.batch_sampler.sampler.set_epoch(epoch)
-
-    @property
-    def batch_idx_in_epoch(self):
-        if self.drop_last:
-            return len(self._index_list) // self.batch_size - (len(self._index_list) - self.data_idx) // self.batch_size
-        else:
-            return (len(self._index_list) + self.batch_size - 1) // self.batch_size - \
-                (len(self._index_list) - self.data_idx + self.batch_size - 1) // self.batch_size
-
-# todo
-# class SortedSampler(ReproducibleIterator):
-#     def __init__(self, dataset, key):
-#         pass
-#
-#
-# class BucketedSampler(ReproducibleIterator):
-#     def __init__(self, dataset, key):
-#         pass
-
-if __name__ == "__main__":
-
-    sampler = RandomSampler(1)
 
-    print(vars(sampler))
 
-    batch_sampler = ReproducibleBatchSampler(list(range(3)), 1, True)
-    print(vars(batch_sampler))
 
 
 
diff --git a/tests/core/drivers/paddle_driver/test_single_device.py b/tests/core/drivers/paddle_driver/test_single_device.py
index 2cb6d5be..33662d7f 100644
--- a/tests/core/drivers/paddle_driver/test_single_device.py
+++ b/tests/core/drivers/paddle_driver/test_single_device.py
@@ -9,7 +9,8 @@ import paddle
 from paddle.io import DataLoader, BatchSampler
 
 from fastNLP.core.drivers.paddle_driver.single_device import PaddleSingleDriver
-from fastNLP.core.samplers.reproducible_sampler import ReproducibleBatchSampler, RandomSampler
+from fastNLP.core.samplers.reproducible_sampler import RandomSampler
+from fastNLP.core.samplers import ReproducibleBatchSampler
 from tests.helpers.models.paddle_model import PaddleNormalModel_Classification
 from tests.helpers.datasets.paddle_data import PaddleDataset_MNIST, PaddleRandomDataset
 from fastNLP.core import synchronize_safe_rm
diff --git a/tests/core/samplers/test_reproducible_batch_sampler.py b/tests/core/samplers/test_reproducible_batch_sampler.py
new file mode 100644
index 00000000..42b86dcd
--- /dev/null
+++ b/tests/core/samplers/test_reproducible_batch_sampler.py
@@ -0,0 +1,439 @@
+from array import array
+
+import numpy as np
+import pytest
+from itertools import chain
+
+from fastNLP.core.samplers import ReproducibleBatchSampler, BucketedBatchSampler
+from fastNLP.core.drivers.torch_driver.utils import replace_batch_sampler
+from tests.helpers.datasets.torch_data import TorchNormalDataset
+
+
+class TestReproducibleBatchSampler:
+    # TODO 拆分测试，在这里只测试一个东西
+    def test_torch_dataloader_1(self):
+        import torch
+        from torch.utils.data import DataLoader
+        # no shuffle
+        before_batch_size = 7
+        dataset = TorchNormalDataset(num_of_data=100)
+        dataloader = DataLoader(dataset, batch_size=before_batch_size)
+        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
+        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
+
+        forward_steps = 3
+        iter_dataloader = iter(dataloader)
+        for _ in range(forward_steps):
+            next(iter_dataloader)
+
+        # 1. 保存状态
+        _get_re_batchsampler = dataloader.batch_sampler
+        assert isinstance(_get_re_batchsampler, ReproducibleBatchSampler)
+        state = _get_re_batchsampler.state_dict()
+        assert state == {"index_list": array("I", list(range(100))), "data_idx": forward_steps*before_batch_size,
+                         "sampler_type": "ReproducibleBatchSampler"}
+
+        # 2. 断点重训，重新生成一个 dataloader；
+        # 不改变 batch_size；
+        dataloader = DataLoader(dataset, batch_size=before_batch_size)
+        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
+        re_batchsampler.load_state_dict(state)
+        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
+
+        real_res = []
+        supposed_res = (torch.tensor(list(range(21, 28))), torch.tensor(list(range(28, 35))))
+        forward_steps = 2
+        iter_dataloader = iter(dataloader)
+        for _ in range(forward_steps):
+            real_res.append(next(iter_dataloader))
+
+        for i in range(forward_steps):
+            assert all(real_res[i] == supposed_res[i])
+
+        # 改变 batch_size；
+        after_batch_size = 3
+        dataloader = DataLoader(dataset, batch_size=after_batch_size)
+        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
+        re_batchsampler.load_state_dict(state)
+        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
+
+        real_res = []
+        supposed_res = (torch.tensor(list(range(21, 24))), torch.tensor(list(range(24, 27))))
+        forward_steps = 2
+        iter_dataloader = iter(dataloader)
+        for _ in range(forward_steps):
+            real_res.append(next(iter_dataloader))
+
+        for i in range(forward_steps):
+            assert all(real_res[i] == supposed_res[i])
+
+        # 断点重训的第二轮是否是一个完整的 dataloader；
+        # 先把断点重训所在的那一个 epoch 跑完；
+        begin_idx = 27
+        while True:
+            try:
+                data = next(iter_dataloader)
+                _batch_size = len(data)
+                assert all(data == torch.tensor(list(range(begin_idx, begin_idx + _batch_size))))
+                begin_idx += _batch_size
+            except StopIteration:
+                break
+
+        # 开始新的一轮；
+        begin_idx = 0
+        iter_dataloader = iter(dataloader)
+        while True:
+            try:
+                data = next(iter_dataloader)
+                _batch_size = len(data)
+                assert all(data == torch.tensor(list(range(begin_idx, begin_idx + _batch_size))))
+                begin_idx += _batch_size
+            except StopIteration:
+                break
+
+    def test_torch_dataloader_2(self):
+        # 测试新的一轮的 index list 是重新生成的，而不是沿用上一轮的；
+        from torch.utils.data import DataLoader
+        # no shuffle
+        before_batch_size = 7
+        dataset = TorchNormalDataset(num_of_data=100)
+        # 开启 shuffle，来检验断点重训后的第二轮的 index list 是不是重新生成的；
+        dataloader = DataLoader(dataset, batch_size=before_batch_size, shuffle=True)
+        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
+        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
+
+        # 将一轮的所有数据保存下来，看是否恢复的是正确的；
+        all_supposed_data = []
+        forward_steps = 3
+        iter_dataloader = iter(dataloader)
+        for _ in range(forward_steps):
+            all_supposed_data.extend(next(iter_dataloader).tolist())
+
+        # 1. 保存状态
+        _get_re_batchsampler = dataloader.batch_sampler
+        assert isinstance(_get_re_batchsampler, ReproducibleBatchSampler)
+        state = _get_re_batchsampler.state_dict()
+
+        # 2. 断点重训，重新生成一个 dataloader；
+        # 不改变 batch_size；
+        dataloader = DataLoader(dataset, batch_size=before_batch_size, shuffle=True)
+        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
+        re_batchsampler.load_state_dict(state)
+        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
+
+        # 先把这一轮的数据过完；
+        pre_index_list = dataloader.batch_sampler.state_dict()["index_list"]
+        while True:
+            try:
+                all_supposed_data.extend(next(iter_dataloader).tolist())
+            except StopIteration:
+                break
+        assert all_supposed_data == list(pre_index_list)
+
+        # 重新开启新的一轮；
+        for _ in range(3):
+            iter_dataloader = iter(dataloader)
+            res = []
+            while True:
+                try:
+                    res.append(next(iter_dataloader))
+                except StopIteration:
+                    break
+
+    def test_3(self):
+        import torch
+        from torch.utils.data import DataLoader
+        before_batch_size = 7
+        dataset = TorchNormalDataset(num_of_data=100)
+        # 开启 shuffle，来检验断点重训后的第二轮的 index list 是不是重新生成的；
+        dataloader = DataLoader(dataset, batch_size=before_batch_size)
+
+        for idx, data in enumerate(dataloader):
+            if idx > 3:
+                break
+
+        iterator = iter(dataloader)
+        for each in iterator:
+            pass
+
+
+class DatasetWithVaryLength:
+    def __init__(self, num_of_data=100):
+        self.data = np.arange(num_of_data)
+
+    def __getitem__(self, item):
+        return self.data[item]
+
+    def __len__(self):
+        return len(self.data)
+
+
+class TestBucketedBatchSampler:
+    @pytest.mark.parametrize('shuffle', [True, False])
+    @pytest.mark.parametrize('drop_last', [True, False])
+    @pytest.mark.parametrize('num', [2, 7, 14, 15, 70, 71])
+    def test_single_num_batch(self, shuffle, drop_last, num):
+        # 数量不够不报错
+        for num in [2, 7, 14, 15, 70, 71]:
+            dataset = DatasetWithVaryLength(num_of_data=num)
+            before_batch_size = 7
+            re_batchsampler = BucketedBatchSampler(dataset, length=dataset.data, batch_size=before_batch_size,
+                                                   num_batch_per_bucket=10, drop_last=drop_last,
+                                                   shuffle=shuffle)
+            count = len(list(iter(re_batchsampler)))
+            if drop_last:
+                assert count==num//before_batch_size, num
+            else:
+                assert count==(num+before_batch_size-1)//before_batch_size, num
+
+    @pytest.mark.parametrize('shuffle', [True, False])
+    @pytest.mark.parametrize('drop_last', [True, False])
+    def test_single(self, shuffle, drop_last):
+
+        before_batch_size = 7
+        num_batch_per_bucket = 4  # 那么任意 batch 内的长度差值不应该超过4
+
+        dataset = DatasetWithVaryLength(num_of_data=1000)
+        re_batchsampler = BucketedBatchSampler(dataset, length=dataset.data, batch_size=before_batch_size,
+                                               num_batch_per_bucket=num_batch_per_bucket, drop_last=drop_last,
+                                               shuffle=shuffle)
+        re_batchsampler.set_epoch(0)
+        forward_steps = 10
+        iterator = iter(re_batchsampler)
+        already_generate_indices = set()
+        for _ in range(forward_steps):
+            batch = next(iterator)
+            assert max(batch) - min(batch) <= before_batch_size * num_batch_per_bucket
+            already_generate_indices.update(batch)
+
+        # 1. 保存状态
+        state = re_batchsampler.state_dict()
+
+        # 2. 断点重训，继续训练
+        re_batchsampler2 = BucketedBatchSampler(dataset, length=dataset.data, batch_size=before_batch_size,
+                                               num_batch_per_bucket=num_batch_per_bucket, drop_last=drop_last,
+                                               shuffle=shuffle)
+        re_batchsampler2.load_state_dict(state)
+        re_batchsampler2.set_epoch(0)
+        new_already_generate_indices = set()
+        mask = np.ones(len(dataset), dtype=bool)
+        mask[list(already_generate_indices)] = 0
+        indices = np.arange(len(dataset))[mask]
+        max_diff = -1
+        for i in range(len(indices)-before_batch_size * num_batch_per_bucket):
+            max_diff = max(max_diff, indices[i+before_batch_size * num_batch_per_bucket]-indices[i])
+        for batch in re_batchsampler2:
+            assert max(batch) - min(batch) <= max_diff
+            for b in batch:
+                assert b not in already_generate_indices
+            new_already_generate_indices.update(batch)
+        if drop_last is False:
+            assert len(new_already_generate_indices.union(already_generate_indices))==len(dataset)
+
+        # 改变 batch_size；
+        after_batch_size = 3
+        re_batchsampler3 = BucketedBatchSampler(dataset, length=dataset.data, batch_size=after_batch_size,
+                                                num_batch_per_bucket=num_batch_per_bucket, drop_last=drop_last,
+                                                shuffle=shuffle)
+        re_batchsampler3.load_state_dict(state)
+        re_batchsampler3.set_epoch(0)
+        count = 0
+
+        mask = np.ones(len(dataset), dtype=bool)
+        mask[list(already_generate_indices)] = 0
+        indices = np.arange(len(dataset))[mask]
+        max_diff = -1
+        for i in range(len(indices)-after_batch_size * num_batch_per_bucket):
+            max_diff = max(max_diff, indices[i+after_batch_size * num_batch_per_bucket]-indices[i])
+
+        for batch in re_batchsampler3:
+            assert max(batch) - min(batch) <= max_diff
+            for b in batch:
+                assert b not in already_generate_indices
+            already_generate_indices.update(batch)
+            count += 1
+            if count > 5:
+                break
+
+        # 再 save ，不允许再上个epoch没结束继续sample
+        after_batch_size = 5
+        with pytest.raises(RuntimeError):
+            state = re_batchsampler3.state_dict()
+
+        for batch in re_batchsampler3:  # consume all, 这样才能save
+            pass
+
+        already_generate_indices = set()
+        count = 0
+        for batch in re_batchsampler3:  # 重新开始
+            assert max(batch) - min(batch) <= max_diff
+            for b in batch:
+                assert b not in already_generate_indices
+            already_generate_indices.update(batch)
+            count += 1
+            if count > 5:
+                break
+
+        state = re_batchsampler3.state_dict()
+        # 这里的 drop_last 为 False，需要最终是所有 sample
+        re_batchsampler4 = BucketedBatchSampler(dataset, length=dataset.data, batch_size=after_batch_size,
+                                                num_batch_per_bucket=num_batch_per_bucket, drop_last=False,
+                                                shuffle=shuffle)
+        re_batchsampler4.load_state_dict(state)
+        re_batchsampler4.set_epoch(0)
+
+        mask = np.ones(len(dataset), dtype=bool)
+        mask[list(already_generate_indices)] = 0
+        indices = np.arange(len(dataset))[mask]
+        max_diff = -1
+        for i in range(len(indices) - after_batch_size * num_batch_per_bucket):
+            max_diff = max(max_diff, indices[i + after_batch_size * num_batch_per_bucket] - indices[i])
+
+        for batch in re_batchsampler4:
+            assert max(batch) - min(batch) <= max_diff
+            for b in batch:
+                assert b not in already_generate_indices
+            already_generate_indices.update(batch)
+
+        assert len(already_generate_indices) == len(dataset)
+
+    @pytest.mark.parametrize('shuffle', [True, False])
+    @pytest.mark.parametrize('drop_last', [True, False])
+    @pytest.mark.parametrize('pad', [True, False])
+    def test_multi(self, shuffle, drop_last, pad):
+    # def test_multi(self, shuffle=True, drop_last=False, pad=False):
+
+        # no shuffle
+        num_replica = 2
+        dataset = DatasetWithVaryLength(num_of_data=1000)
+        batch_size = 5
+        num_batch_per_bucket = 10
+        lengths = []
+        rank0_already_seen_indexes = None
+        max_diff = num_batch_per_bucket * batch_size * num_replica
+        for rank in range(num_replica):
+            sampler = BucketedBatchSampler(dataset, length=dataset.data, batch_size = batch_size,
+                                           num_batch_per_bucket = num_batch_per_bucket,
+                                           shuffle = shuffle, drop_last=drop_last)
+            sampler.set_epoch(0)
+            sampler.set_distributed(num_replica, rank=rank, pad=pad)
+            lengths.append(len(sampler))
+            already_seen_indexes = set()
+            repeat_count = 0
+            for batch in sampler:
+                assert max_diff>=max(batch)-min(batch)
+                for b in batch:
+                    repeat_count += int(b in already_seen_indexes)
+                    if rank0_already_seen_indexes:  # 不能交叉出现
+                        assert b not in rank0_already_seen_indexes
+                already_seen_indexes.update(batch)
+            if rank0_already_seen_indexes is None:
+                rank0_already_seen_indexes = already_seen_indexes
+            if pad:  # 应该允许重复一次
+                assert repeat_count<=1
+            else:
+                assert repeat_count==0
+
+        assert len(set(lengths))==1, lengths  # 每个进程的batch数量一致
+
+        # 多进程的保存
+        already_seen_indexes = set()
+        for rank in range(num_replica):
+            sampler = BucketedBatchSampler(dataset, length=dataset.data, batch_size = batch_size,
+                                           num_batch_per_bucket = num_batch_per_bucket,
+                                           shuffle = shuffle, drop_last=drop_last)
+            sampler.set_epoch(0)
+            sampler.set_distributed(num_replica, rank=rank, pad=pad)
+            lengths.append(len(sampler))
+            count = 0
+            for batch in sampler:
+                assert max_diff>=max(batch)-min(batch)
+                already_seen_indexes.update(batch)
+                if count>5:
+                    break
+                count += 1
+            state = sampler.state_dict()
+
+        # 切换成单机
+        new_batch_size = 6
+        num_batch_per_bucket = 3
+        new_sampler = BucketedBatchSampler(dataset, length=dataset.data, batch_size=new_batch_size,
+                                           num_batch_per_bucket=num_batch_per_bucket,
+                                           shuffle=shuffle, drop_last=drop_last)
+        new_sampler.load_state_dict(state)
+        repeat_count = 0
+        new_already_seen_indexes = set(list(already_seen_indexes))
+
+        mask = np.ones(len(dataset), dtype=bool)
+        mask[list(already_seen_indexes)] = 0
+        indices = np.arange(len(dataset))[mask]
+        max_diff = -1
+        for i in range(len(indices)-new_batch_size * num_batch_per_bucket):
+            max_diff = max(max_diff, indices[i+new_batch_size * num_batch_per_bucket]-indices[i])
+
+        for batch in new_sampler:
+            assert max_diff>=max(batch)-min(batch)
+            for b in batch:
+                repeat_count += int(b in new_already_seen_indexes)
+            new_already_seen_indexes.update(batch)
+        if pad:  # 应该允许重复一次
+            assert repeat_count <= 1
+        else:
+            assert repeat_count == 0
+        if drop_last is False:  # 如果没有drop应该相等
+            assert len(new_already_seen_indexes)==len(dataset)
+
+        # 测试替换卡的数量。
+        num_replica = 3
+        new_sampler = BucketedBatchSampler(dataset, length=dataset.data, batch_size=new_batch_size,
+                                           num_batch_per_bucket=num_batch_per_bucket,
+                                           shuffle=shuffle, drop_last=drop_last)
+        new_sampler.set_epoch(0)
+        new_sampler.load_state_dict(state)
+        new_sampler.set_distributed(num_replicas=num_replica, rank=1, pad=pad)
+        repeat_count = 0
+
+        mask = np.ones(len(dataset), dtype=bool)
+        mask[list(already_seen_indexes)] = 0
+        indices = np.arange(len(dataset))[mask]
+        max_diff = -1
+        for i in range(len(indices) - new_batch_size * num_batch_per_bucket*num_replica):
+            max_diff = max(max_diff, indices[i + new_batch_size * num_batch_per_bucket*num_replica] - indices[i])
+
+        for batch in new_sampler:
+            assert max_diff>=max(batch)-min(batch)
+            for b in batch:
+                repeat_count += int(b in already_seen_indexes)
+        if pad:  # 应该允许重复一次
+            assert repeat_count <= 1
+        else:
+            assert repeat_count == 0
+
+    @pytest.mark.parametrize('shuffle', [True, False])
+    @pytest.mark.parametrize('drop_last', [True, False])
+    @pytest.mark.parametrize('pad', [True, False])
+    @pytest.mark.parametrize('num_samples', [13, 100, 623, 1000])
+    @pytest.mark.parametrize('num_replica', [2, 3])
+    def test_multi_same_bucket(self, shuffle, drop_last, pad, num_samples, num_replica):
+    # def test_multi_same_bucket(self, shuffle=True, drop_last=True, pad=True, num_samples=623, num_replica=2):
+        # TODO 两个 rank 上的长度是要在同一个bucket的
+        dataset = DatasetWithVaryLength(num_of_data=num_samples)
+        batch_size = 6
+        if num_replica*batch_size > num_samples:
+            return
+        num_batch_per_bucket = 10
+        samplers = []
+        lengths = []
+        for i in range(num_replica):
+            sampler = BucketedBatchSampler(dataset, length=dataset.data, batch_size=batch_size,
+                                            num_batch_per_bucket=num_batch_per_bucket, shuffle=shuffle, drop_last=drop_last)
+            sampler.set_distributed(num_replica, rank=i, pad=pad)
+            sampler.set_epoch(0)
+            samplers.append(sampler)
+            lengths.append(len(list(iter(sampler))))
+        assert len(set(lengths))==1
+        bucket_diff = batch_size * num_batch_per_bucket * num_replica
+
+        for bs in zip(*samplers):
+            diff = max(chain(*bs)) - min(chain(*bs))
+            assert diff <= bucket_diff
diff --git a/tests/core/samplers/test_reproducible_sampler.py b/tests/core/samplers/test_reproducible_sampler.py
index 88cc7444..0a3697d3 100644
--- a/tests/core/samplers/test_reproducible_sampler.py
+++ b/tests/core/samplers/test_reproducible_sampler.py
@@ -6,7 +6,7 @@ import numpy as np
 from functools import partial
 from array import array
 
-from fastNLP.core.samplers.reproducible_sampler import RandomSampler, ReproducibleBatchSampler
+from fastNLP.core.samplers.reproducible_sampler import RandomSampler
 from fastNLP.core.drivers.torch_driver.utils import replace_batch_sampler
 from tests.helpers.datasets.torch_data import TorchNormalDataset
 
@@ -361,148 +361,3 @@ class TestRandomSampler(unittest.TestCase):
 
 
 
-class TestReproducibleBatchSampler:
-    def test_torch_dataloader_1(self):
-        import torch
-        from torch.utils.data import DataLoader
-        # no shuffle
-        before_batch_size = 7
-        dataset = TorchNormalDataset(num_of_data=100)
-        dataloader = DataLoader(dataset, batch_size=before_batch_size)
-        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
-        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
-
-        forward_steps = 3
-        iter_dataloader = iter(dataloader)
-        for _ in range(forward_steps):
-            next(iter_dataloader)
-
-        # 1. 保存状态
-        _get_re_batchsampler = dataloader.batch_sampler
-        assert isinstance(_get_re_batchsampler, ReproducibleBatchSampler)
-        state = _get_re_batchsampler.state_dict()
-        assert state == {"index_list": array("I", list(range(100))), "data_idx": forward_steps*before_batch_size,
-                         "sampler_type": "ReproducibleBatchSampler"}
-
-        # 2. 断点重训，重新生成一个 dataloader；
-        # 不改变 batch_size；
-        dataloader = DataLoader(dataset, batch_size=before_batch_size)
-        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
-        re_batchsampler.load_state_dict(state)
-        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
-
-        real_res = []
-        supposed_res = (torch.tensor(list(range(21, 28))), torch.tensor(list(range(28, 35))))
-        forward_steps = 2
-        iter_dataloader = iter(dataloader)
-        for _ in range(forward_steps):
-            real_res.append(next(iter_dataloader))
-
-        for i in range(forward_steps):
-            assert all(real_res[i] == supposed_res[i])
-
-        # 改变 batch_size；
-        after_batch_size = 3
-        dataloader = DataLoader(dataset, batch_size=after_batch_size)
-        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
-        re_batchsampler.load_state_dict(state)
-        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
-
-        real_res = []
-        supposed_res = (torch.tensor(list(range(21, 24))), torch.tensor(list(range(24, 27))))
-        forward_steps = 2
-        iter_dataloader = iter(dataloader)
-        for _ in range(forward_steps):
-            real_res.append(next(iter_dataloader))
-
-        for i in range(forward_steps):
-            assert all(real_res[i] == supposed_res[i])
-
-        # 断点重训的第二轮是否是一个完整的 dataloader；
-        # 先把断点重训所在的那一个 epoch 跑完；
-        begin_idx = 27
-        while True:
-            try:
-                data = next(iter_dataloader)
-                _batch_size = len(data)
-                assert all(data == torch.tensor(list(range(begin_idx, begin_idx + _batch_size))))
-                begin_idx += _batch_size
-            except StopIteration:
-                break
-
-        # 开始新的一轮；
-        begin_idx = 0
-        iter_dataloader = iter(dataloader)
-        while True:
-            try:
-                data = next(iter_dataloader)
-                _batch_size = len(data)
-                assert all(data == torch.tensor(list(range(begin_idx, begin_idx + _batch_size))))
-                begin_idx += _batch_size
-            except StopIteration:
-                break
-
-    def test_torch_dataloader_2(self):
-        # 测试新的一轮的 index list 是重新生成的，而不是沿用上一轮的；
-        from torch.utils.data import DataLoader
-        # no shuffle
-        before_batch_size = 7
-        dataset = TorchNormalDataset(num_of_data=100)
-        # 开启 shuffle，来检验断点重训后的第二轮的 index list 是不是重新生成的；
-        dataloader = DataLoader(dataset, batch_size=before_batch_size, shuffle=True)
-        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
-        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
-
-        # 将一轮的所有数据保存下来，看是否恢复的是正确的；
-        all_supposed_data = []
-        forward_steps = 3
-        iter_dataloader = iter(dataloader)
-        for _ in range(forward_steps):
-            all_supposed_data.extend(next(iter_dataloader).tolist())
-
-        # 1. 保存状态
-        _get_re_batchsampler = dataloader.batch_sampler
-        assert isinstance(_get_re_batchsampler, ReproducibleBatchSampler)
-        state = _get_re_batchsampler.state_dict()
-
-        # 2. 断点重训，重新生成一个 dataloader；
-        # 不改变 batch_size；
-        dataloader = DataLoader(dataset, batch_size=before_batch_size, shuffle=True)
-        re_batchsampler = ReproducibleBatchSampler(dataloader.batch_sampler, dataloader.batch_size, drop_last=False)
-        re_batchsampler.load_state_dict(state)
-        dataloader = replace_batch_sampler(dataloader, re_batchsampler)
-
-        # 先把这一轮的数据过完；
-        pre_index_list = dataloader.batch_sampler.state_dict()["index_list"]
-        while True:
-            try:
-                all_supposed_data.extend(next(iter_dataloader).tolist())
-            except StopIteration:
-                break
-        assert all_supposed_data == list(pre_index_list)
-
-        # 重新开启新的一轮；
-        for _ in range(3):
-            iter_dataloader = iter(dataloader)
-            res = []
-            while True:
-                try:
-                    res.append(next(iter_dataloader))
-                except StopIteration:
-                    break
-
-    def test_3(self):
-        import torch
-        from torch.utils.data import DataLoader, RandomSampler, BatchSampler
-        before_batch_size = 7
-        dataset = TorchNormalDataset(num_of_data=100)
-        # 开启 shuffle，来检验断点重训后的第二轮的 index list 是不是重新生成的；
-        dataloader = DataLoader(dataset, batch_size=before_batch_size)
-
-        for idx, data in enumerate(dataloader):
-            if idx > 3:
-                break
-
-        iterator = iter(dataloader)
-        for each in iterator:
-            pass