diff --git a/fastNLP/api/pos_tagger.py b/fastNLP/api/pos_tagger.py
new file mode 100644
index 00000000..fbd689c1
--- /dev/null
+++ b/fastNLP/api/pos_tagger.py
@@ -0,0 +1,44 @@
+import pickle
+
+import numpy as np
+
+from fastNLP.core.dataset import DataSet
+from fastNLP.loader.model_loader import ModelLoader
+from fastNLP.core.predictor import Predictor
+
+
+class POS_tagger:
+    def __init__(self):
+        pass
+
+    def predict(self, query):
+        """ 
+        :param query: List[str]
+        :return answer: List[str]
+
+        """
+        # TODO: 根据query 构建DataSet
+        pos_dataset = DataSet()
+        pos_dataset["text_field"] = np.array(query)
+
+        # 加载pipeline和model
+        pipeline = self.load_pipeline("./xxxx")
+
+        # 将DataSet作为参数运行 pipeline
+        pos_dataset = pipeline(pos_dataset)
+
+        # 加载模型
+        model = ModelLoader().load_pytorch("./xxx")
+
+        # 调 predictor
+        predictor = Predictor()
+        output = predictor.predict(model, pos_dataset)
+
+        # TODO: 转成最终输出
+        return None
+
+    @staticmethod
+    def load_pipeline(path):
+        with open(path, "r") as fp:
+            pipeline = pickle.load(fp)
+        return pipeline
diff --git a/fastNLP/core/batch.py b/fastNLP/core/batch.py
index 0381d267..397a3ddb 100644
--- a/fastNLP/core/batch.py
+++ b/fastNLP/core/batch.py
@@ -56,8 +56,8 @@ class Batch(object):
             indices = self.idx_list[self.curidx:endidx]
 
             for field_name, field in self.dataset.get_fields():
-                batch = field.get(indices)
-                if not field.tensorable: #TODO 修改
+                batch = torch.from_numpy(field.get(indices))
+                if not field.need_tensor: #TODO 修改
                     pass
                 elif field.is_target:
                     batch_y[field_name] = batch
diff --git a/fastNLP/core/dataset.py b/fastNLP/core/dataset.py
index c2a10210..e626ff26 100644
--- a/fastNLP/core/dataset.py
+++ b/fastNLP/core/dataset.py
@@ -2,10 +2,12 @@ import random
 import sys
 from collections import defaultdict
 from copy import deepcopy
+import numpy as np
 
 from fastNLP.core.field import TextField, LabelField
 from fastNLP.core.instance import Instance
 from fastNLP.core.vocabulary import Vocabulary
+from fastNLP.core.fieldarray import FieldArray
 
 _READERS = {}
 
@@ -14,43 +16,36 @@ class DataSet(object):
 
     """
 
-    def __init__(self, fields=None):
-        """
-
-        """
-        pass
-
-    def index_all(self, vocab):
-        for ins in self:
-            ins.index_all(vocab)
-        return self
+    def __init__(self, instance=None):
+        if instance is not None:
+            self._convert_ins(instance)
+        else:
+            self.field_arrays = {}
 
-    def index_field(self, field_name, vocab):
-        if isinstance(field_name, str):
-            field_list = [field_name]
-            vocab_list = [vocab]
+    def _convert_ins(self, ins_list):
+        if isinstance(ins_list, list):
+            for ins in ins_list:
+                self.append(ins)
         else:
-            classes = (list, tuple)
-            assert isinstance(field_name, classes) and isinstance(vocab, classes) and len(field_name) == len(vocab)
-            field_list = field_name
-            vocab_list = vocab
-
-        for name, vocabs in zip(field_list, vocab_list):
-            for ins in self:
-                ins.index_field(name, vocabs)
-        return self
+            self.append(ins)
 
-    def to_tensor(self, idx: int, padding_length: dict):
-        """Convert an instance in a dataset to tensor.
+    def append(self, ins):
+        # no field
+        if len(self.field_arrays) == 0:
+            for name, field in ins.field.items():
+                self.field_arrays[name] = FieldArray(name, [field])
+        else:
+            assert len(self.field_arrays) == len(ins.field)
+            for name, field in ins.field.items():
+                assert name in self.field_arrays
+                self.field_arrays[name].append(field)
 
-        :param idx: int, the index of the instance in the dataset.
-        :param padding_length: int
-        :return tensor_x: dict of (str: torch.LongTensor), which means (field name: tensor of shape [padding_length, ])
-                tensor_y: dict of (str: torch.LongTensor), which means (field name: tensor of shape [padding_length, ])
+    def get_fields(self):
+        return self.field_arrays
 
-        """
-        ins = self[idx]
-        return ins.to_tensor(padding_length, self.origin_len)
+    def __len__(self):
+        field = self.field_arrays.values()[0]
+        return len(field)
 
     def get_length(self):
         """Fetch lengths of all fields in all instances in a dataset.
@@ -59,15 +54,10 @@ class DataSet(object):
                 The list contains lengths of this field in all instances.
 
         """
-        lengths = defaultdict(list)
-        for ins in self:
-            for field_name, field_length in ins.get_length().items():
-                lengths[field_name].append(field_length)
-        return lengths
+        pass
 
     def shuffle(self):
-        random.shuffle(self)
-        return self
+        pass
 
     def split(self, ratio, shuffle=True):
         """Train/dev splitting
@@ -78,58 +68,37 @@ class DataSet(object):
                 dev_set: a DataSet object, representing the validation set
 
         """
-        assert 0 < ratio < 1
-        if shuffle:
-            self.shuffle()
-        split_idx = int(len(self) * ratio)
-        dev_set = deepcopy(self)
-        train_set = deepcopy(self)
-        del train_set[:split_idx]
-        del dev_set[split_idx:]
-        return train_set, dev_set
+        pass
 
     def rename_field(self, old_name, new_name):
         """rename a field
         """
-        for ins in self:
-            ins.rename_field(old_name, new_name)
+        if old_name in self.field_arrays:
+            self.field_arrays[new_name] = self.field_arrays.pop(old_name)
+        else:
+            raise KeyError
         return self
 
-    def set_target(self, **fields):
+    def set_is_target(self, **fields):
         """Change the flag of `is_target` for all instance. For fields not set here, leave their `is_target` unchanged.
 
-        :param key-value pairs for field-name and `is_target` value(True, False or None).
-        """
-        for ins in self:
-            ins.set_target(**fields)
-        return self
-
-    def update_vocab(self, **name_vocab):
-        """using certain field data to update vocabulary.
-
-        e.g. ::
-
-            # update word vocab and label vocab seperately
-            dataset.update_vocab(word_seq=word_vocab, label_seq=label_vocab)
+        :param key-value pairs for field-name and `is_target` value(True, False).
         """
-        for field_name, vocab in name_vocab.items():
-            for ins in self:
-                vocab.update(ins[field_name].contents())
+        for name, val in fields.items():
+            if name in self.field_arrays:
+                assert isinstance(val, bool)
+                self.field_arrays[name].is_target = val
+            else:
+                raise KeyError
         return self
 
-    def set_origin_len(self, origin_field, origin_len_name=None):
-        """make dataset tensor output contain origin_len field.
-
-        e.g. ::
-
-            # output "word_seq_origin_len", lengths based on "word_seq" field
-            dataset.set_origin_len("word_seq")
-        """
-        if origin_field is None:
-            self.origin_len = None
-        else:
-            self.origin_len = (origin_field + "_origin_len", origin_field) \
-                if origin_len_name is None else (origin_len_name, origin_field)
+    def set_need_tensor(self, **kwargs):
+        for name, val in kwargs.items():
+            if name in self.field_arrays:
+                assert isinstance(val, bool)
+                self.field_arrays[name].need_tensor = val
+            else:
+                raise KeyError
         return self
 
     def __getattribute__(self, name):
diff --git a/fastNLP/core/field.py b/fastNLP/core/field.py
index 8720bf1b..5b9c1b63 100644
--- a/fastNLP/core/field.py
+++ b/fastNLP/core/field.py
@@ -7,10 +7,9 @@ class Field(object):
 
     """
 
-    def __init__(self, name, is_target: bool):
-        self.name = name
+    def __init__(self, content, is_target: bool):
         self.is_target = is_target
-        self.content = None
+        self.content = content
 
     def index(self, vocab):
         """create index field
@@ -29,23 +28,15 @@ class Field(object):
         raise NotImplementedError
 
     def __repr__(self):
-        return self.contents().__repr__()
-
-    def new(self, *args, **kwargs):
-        return self.__class__(*args, **kwargs, is_target=self.is_target)
+        return self.content.__repr__()
 
 class TextField(Field):
-    def __init__(self, name, text, is_target):
+    def __init__(self, text, is_target):
         """
         :param text: list of strings
         :param is_target: bool
         """
-        super(TextField, self).__init__(name, is_target)
-        self.content = text
-
-    def index(self, vocab):
-        idx_field = IndexField(self.name+'_idx', self.content, vocab, self.is_target)
-        return idx_field
+        super(TextField, self).__init__(text, is_target)
 
 
 class IndexField(Field):
@@ -82,75 +73,19 @@ class LabelField(Field):
 
     """
     def __init__(self, label, is_target=True):
-        super(LabelField, self).__init__(is_target)
-        self.label = label
-        self._index = None
+        super(LabelField, self).__init__(label, is_target)
 
-    def get_length(self):
-        """Fetch the length of the label field.
-
-        :return length: int, the length of the label, always 1.
-        """
-        return 1
-
-    def index(self, vocab):
-        if self._index is None:
-            if isinstance(self.label, str):
-                self._index = vocab[self.label]
-        return self._index
-
-    def to_tensor(self, padding_length):
-        if self._index is None:
-            if isinstance(self.label, int):
-                return torch.tensor(self.label)
-            elif isinstance(self.label, str):
-                raise RuntimeError("Field {} not indexed. Call index method.".format(self.label))
-            else:
-                raise RuntimeError(
-                    "Not support type for LabelField. Expect str or int, got {}.".format(type(self.label)))
-        else:
-            return torch.LongTensor([self._index])
-
-    def contents(self):
-        return [self.label]
 
 class SeqLabelField(Field):
     def __init__(self, label_seq, is_target=True):
-        super(SeqLabelField, self).__init__(is_target)
-        self.label_seq = label_seq
-        self._index = None
-
-    def get_length(self):
-        return len(self.label_seq)
-
-    def index(self, vocab):
-        if self._index is None:
-            self._index = [vocab[c] for c in self.label_seq]
-        return self._index
-
-    def to_tensor(self, padding_length):
-        pads = [0] * (padding_length - self.get_length())
-        if self._index is None:
-            if self.get_length() == 0:
-                return torch.LongTensor(pads)
-            elif isinstance(self.label_seq[0], int):
-                return torch.LongTensor(self.label_seq + pads)
-            elif isinstance(self.label_seq[0], str):
-                raise RuntimeError("Field {} not indexed. Call index method.".format(self.label))
-            else:
-                raise RuntimeError(
-                    "Not support type for SeqLabelField. Expect str or int, got {}.".format(type(self.label)))
-        else:
-            return torch.LongTensor(self._index + pads)
-
-    def contents(self):
-        return self.label_seq.copy()
+        super(SeqLabelField, self).__init__(label_seq, is_target)
 
 
 class CharTextField(Field):
     def __init__(self, text, max_word_len, is_target=False):
         super(CharTextField, self).__init__(is_target)
-        self.text = text
+        # TODO
+        raise NotImplementedError
         self.max_word_len = max_word_len
         self._index = []
 
diff --git a/fastNLP/core/fieldarray.py b/fastNLP/core/fieldarray.py
new file mode 100644
index 00000000..9710f991
--- /dev/null
+++ b/fastNLP/core/fieldarray.py
@@ -0,0 +1,39 @@
+import torch
+import numpy as np
+
+class FieldArray(object):
+    def __init__(self, name, content, padding_val=0, is_target=True, need_tensor=True):
+        self.name = name
+        self.data = [self._convert_np(val) for val in content]
+        self.padding_val = padding_val
+        self.is_target = is_target
+        self.need_tensor = need_tensor
+
+    def _convert_np(self, val):
+        if not isinstance(val, np.array):
+            return np.array(val)
+        else:
+            return val
+
+    def append(self, val):
+        self.data.append(self._convert_np(val))
+
+    def get(self, idxes):
+        if isinstance(idxes, int):
+            return self.data[idxes]
+        elif isinstance(idxes, list):
+            id_list = np.array(idxes)
+        batch_size = len(id_list)
+        len_list = [(i, self.data[i].shape[0]) for i in id_list]
+        _, max_len = max(len_list, key=lambda x: x[1])
+        array = np.full((batch_size, max_len), self.padding_val, dtype=np.int32)
+
+        for i, (idx, length) in enumerate(len_list):
+            if length == max_len:
+                array[i] = self.data[idx]
+            else:
+                array[i][:length] = self.data[idx]
+        return array
+
+    def __len__(self):
+        return len(self.data)
diff --git a/fastNLP/core/instance.py b/fastNLP/core/instance.py
index 50787fd1..a2686da8 100644
--- a/fastNLP/core/instance.py
+++ b/fastNLP/core/instance.py
@@ -7,8 +7,6 @@ class Instance(object):
 
     def __init__(self, **fields):
         self.fields = fields
-        self.has_index = False
-        self.indexes = {}
 
     def add_field(self, field_name, field):
         self.fields[field_name] = field
@@ -17,8 +15,6 @@ class Instance(object):
     def rename_field(self, old_name, new_name):
         if old_name in self.fields:
             self.fields[new_name] = self.fields.pop(old_name)
-            if old_name in self.indexes:
-                self.indexes[new_name] = self.indexes.pop(old_name)
         else:
             raise KeyError("error, no such field: {}".format(old_name))
         return self
@@ -38,53 +34,5 @@ class Instance(object):
     def __setitem__(self, name, field):
         return self.add_field(name, field)
 
-    def get_length(self):
-        """Fetch the length of all fields in the instance.
-
-        :return length: dict of (str: int), which means (field name: field length).
-
-        """
-        length = {name: field.get_length() for name, field in self.fields.items()}
-        return length
-
-    def index_field(self, field_name, vocab):
-        """use `vocab` to index certain field
-        """
-        self.indexes[field_name] = self.fields[field_name].index(vocab)
-        return self
-
-    def index_all(self, vocab):
-        """use `vocab` to index all fields
-        """
-        if self.has_index:
-            print("error")
-            return self.indexes
-        indexes = {name: field.index(vocab) for name, field in self.fields.items()}
-        self.indexes = indexes
-        return indexes
-
-    def to_tensor(self, padding_length: dict, origin_len=None):
-        """Convert instance to tensor.
-
-        :param padding_length: dict of (str: int), which means (field name: padding_length of this field)
-        :return tensor_x: dict of (str: torch.LongTensor), which means (field name: tensor of shape [padding_length, ])
-                tensor_y: dict of (str: torch.LongTensor), which means (field name: tensor of shape [padding_length, ])
-                        If is_target is False for all fields, tensor_y would be an empty dict.
-        """
-        tensor_x = {}
-        tensor_y = {}
-        for name, field in self.fields.items():
-            if field.is_target is True:
-                tensor_y[name] = field.to_tensor(padding_length[name])
-            elif field.is_target is False:
-                tensor_x[name] = field.to_tensor(padding_length[name])
-            else:
-                # is_target is None
-                continue
-        if origin_len is not None:
-            name, field_name = origin_len
-            tensor_x[name] = torch.LongTensor([self.fields[field_name].get_length()])
-        return tensor_x, tensor_y
-
     def __repr__(self):
         return self.fields.__repr__()
\ No newline at end of file
diff --git a/fastNLP/core/predictor.py b/fastNLP/core/predictor.py
index c5d22df4..63e5b7ca 100644
--- a/fastNLP/core/predictor.py
+++ b/fastNLP/core/predictor.py
@@ -2,9 +2,7 @@ import numpy as np
 import torch
 
 from fastNLP.core.batch import Batch
-from fastNLP.core.preprocess import load_pickle
 from fastNLP.core.sampler import SequentialSampler
-from fastNLP.loader.dataset_loader import convert_seq2seq_dataset, convert_seq2tag_dataset, convert_seq_dataset
 
 
 class Predictor(object):
@@ -16,19 +14,9 @@ class Predictor(object):
     Currently, Predictor does not support GPU.
     """
 
-    def __init__(self, pickle_path, post_processor):
-        """
-
-        :param pickle_path: str, the path to the pickle files.
-        :param post_processor: a function or callable object, that takes list of batch outputs as input
-
-        """
+    def __init__(self):
         self.batch_size = 1
         self.batch_output = []
-        self.pickle_path = pickle_path
-        self._post_processor = post_processor
-        self.label_vocab = load_pickle(self.pickle_path, "label2id.pkl")
-        self.word_vocab = load_pickle(self.pickle_path, "word2id.pkl")
 
     def predict(self, network, data):
         """Perform inference using the trained model.
@@ -37,9 +25,6 @@ class Predictor(object):
         :param data: a DataSet object.
         :return: list of list of strings, [num_examples, tag_seq_length]
         """
-        # transform strings into DataSet object
-        # data = self.prepare_input(data)
-
         # turn on the testing mode; clean up the history
         self.mode(network, test=True)
         batch_output = []
@@ -51,7 +36,7 @@ class Predictor(object):
                 prediction = self.data_forward(network, batch_x)
             batch_output.append(prediction)
 
-        return self._post_processor(batch_output, self.label_vocab)
+        return batch_output
 
     def mode(self, network, test=True):
         if test:
@@ -64,37 +49,19 @@ class Predictor(object):
         y = network(**x)
         return y
 
-    def prepare_input(self, data):
-        """Transform two-level list of strings into an DataSet object.
-        In the training pipeline, this is done by Preprocessor. But in inference time, we do not call Preprocessor.
-
-        :param data: list of list of strings.
-                ::
-                [
-                    [word_11, word_12, ...],
-                    [word_21, word_22, ...],
-                    ...
-                ]
-
-        :return data_set: a DataSet instance.
-        """
-        assert isinstance(data, list)
-        data = convert_seq_dataset(data)
-        data.index_field("word_seq", self.word_vocab)
-
 
 class SeqLabelInfer(Predictor):
     def __init__(self, pickle_path):
         print(
             "[FastNLP Warning] SeqLabelInfer will be deprecated. Please use Predictor directly.")
-        super(SeqLabelInfer, self).__init__(pickle_path, seq_label_post_processor)
+        super(SeqLabelInfer, self).__init__()
 
 
 class ClassificationInfer(Predictor):
     def __init__(self, pickle_path):
         print(
             "[FastNLP Warning] ClassificationInfer will be deprecated. Please use Predictor directly.")
-        super(ClassificationInfer, self).__init__(pickle_path, text_classify_post_processor)
+        super(ClassificationInfer, self).__init__()
 
 
 def seq_label_post_processor(batch_outputs, label_vocab):
diff --git a/fastNLP/loader/model_loader.py b/fastNLP/loader/model_loader.py
index c07576b8..5c8a1371 100644
--- a/fastNLP/loader/model_loader.py
+++ b/fastNLP/loader/model_loader.py
@@ -8,8 +8,8 @@ class ModelLoader(BaseLoader):
         Loader for models.
     """
 
-    def __init__(self, data_path):
-        super(ModelLoader, self).__init__(data_path)
+    def __init__(self):
+        super(ModelLoader, self).__init__()
 
     @staticmethod
     def load_pytorch(empty_model, model_path):
@@ -19,3 +19,10 @@ class ModelLoader(BaseLoader):
         :param model_path: str, the path to the saved model.
         """
         empty_model.load_state_dict(torch.load(model_path))
+        
+    @staticmethod
+    def load_pytorch(model_path):
+        """Load the entire model.
+
+        """
+        return torch.load(model_path)
\ No newline at end of file
diff --git a/fastNLP/models/sequence_modeling.py b/fastNLP/models/sequence_modeling.py
index 464f99be..11e49ee1 100644
--- a/fastNLP/models/sequence_modeling.py
+++ b/fastNLP/models/sequence_modeling.py
@@ -127,7 +127,8 @@ class AdvSeqLabel(SeqLabeling):
         :param word_seq: LongTensor, [batch_size, mex_len]
         :param word_seq_origin_len: list of int.
         :param truth: LongTensor, [batch_size, max_len]
-        :return y:
+        :return y: If truth is None, return list of [decode path(list)]. Used in testing and predicting.
+                   If truth is not None, return loss, a scalar. Used in training.
         """
         self.mask = self.make_mask(word_seq, word_seq_origin_len)
 
diff --git a/fastNLP/saver/model_saver.py b/fastNLP/saver/model_saver.py
index 74518a44..fd391f69 100644
--- a/fastNLP/saver/model_saver.py
+++ b/fastNLP/saver/model_saver.py
@@ -15,10 +15,14 @@ class ModelSaver(object):
         """
         self.save_path = save_path
 
-    def save_pytorch(self, model):
+    def save_pytorch(self, model, param_only=True):
         """Save a pytorch model into .pkl file.
 
         :param model: a PyTorch model
+        :param param_only: bool, whether only to save the model parameters or the entire model.
 
         """
-        torch.save(model.state_dict(), self.save_path)
+        if param_only is True:
+            torch.save(model.state_dict(), self.save_path)
+        else:
+            torch.save(model, self.save_path)
diff --git a/reproduction/pos_tag_model/train_pos_tag.py b/reproduction/pos_tag_model/train_pos_tag.py
index 45cfbbc0..fb077fe3 100644
--- a/reproduction/pos_tag_model/train_pos_tag.py
+++ b/reproduction/pos_tag_model/train_pos_tag.py
@@ -59,42 +59,37 @@ def infer():
     print("Inference finished!")
 
 
-def train():
-    # Config Loader
-    train_args = ConfigSection()
-    test_args = ConfigSection()
-    ConfigLoader("good_name").load_config(cfgfile, {"train": train_args, "test": test_args})
+def train(): 
+    # load config
+    trainer_args = ConfigSection()
+    model_args = ConfigSection()
+    ConfigLoader().load_config(cfgfile, {"train": train_args, "test": test_args})
 
     # Data Loader
     loader = PeopleDailyCorpusLoader()
     train_data, _ = loader.load()
 
-    # Preprocessor
-    preprocessor = SeqLabelPreprocess()
-    data_train, data_dev = preprocessor.run(train_data, pickle_path=pickle_path, train_dev_split=0.3)
-    train_args["vocab_size"] = preprocessor.vocab_size
-    train_args["num_classes"] = preprocessor.num_classes
+    # TODO: define processors
+    
+    # define pipeline
+    pp = Pipeline()
+    # TODO: pp.add_processor()
 
-    # Trainer
-    trainer = SeqLabelTrainer(**train_args.data)
+    # run the pipeline, get data_set
+    train_data = pp(train_data)
 
-    # Model
+    # define a model
     model = AdvSeqLabel(train_args)
-    try:
-        ModelLoader.load_pytorch(model, "./save/saved_model.pkl")
-        print('model parameter loaded!')
-    except Exception as e:
-        print("No saved model. Continue.")
-        pass
 
-    # Start training
+    # call trainer to train
+    trainer = SeqLabelTrainer(train_args)
     trainer.train(model, data_train, data_dev)
-    print("Training finished!")
 
-    # Saver
-    saver = ModelSaver("./save/saved_model.pkl")
-    saver.save_pytorch(model)
-    print("Model saved!")
+    # save model
+    ModelSaver("./saved_model.pkl").save_pytorch(model, param_only=False)
+
+    # TODO:save pipeline
+
 
 
 def test():
diff --git a/requirements.txt b/requirements.txt
index 954dd741..a775c8ed 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
 numpy>=1.14.2
-torch==0.4.0
+torch>=0.4.0
 torchvision>=0.1.8
 tensorboardX