diff --git a/fastNLP/core/action.py b/fastNLP/core/action.py
index f3fe5f41..560fa42e 100644
--- a/fastNLP/core/action.py
+++ b/fastNLP/core/action.py
@@ -5,6 +5,7 @@
 from collections import Counter
 
 import numpy as np
+import torch
 
 
 class Action(object):
@@ -21,7 +22,7 @@ class Action(object):
         super(Action, self).__init__()
 
     @staticmethod
-    def make_batch(iterator, data, output_length=True):
+    def make_batch(iterator, data, use_cuda, output_length=True, max_len=None):
         """Batch and Pad data.
         :param iterator: an iterator, (object that implements __next__ method) which returns the next sample.
         :param data: list. Each entry is a sample, which is also a list of features and label(s).
@@ -31,7 +32,9 @@ class Action(object):
                     [[word_21, word_22, word_23], [label_21. label_22]],  # sample 2
                     ...
                 ]
+        :param use_cuda: bool
         :param output_length: whether to output the original length of the sequence before padding.
+        :param max_len: int, maximum sequence length
         :return (batch_x, seq_len): tuple of two elements, if output_length is true.
                      batch_x: list. Each entry is a list of features of a sample. [batch_size, max_len]
                      seq_len: list. The length of the pre-padded sequence, if output_length is True.
@@ -43,13 +46,25 @@ class Action(object):
             batch = [data[idx] for idx in indices]
             batch_x = [sample[0] for sample in batch]
             batch_y = [sample[1] for sample in batch]
-            batch_x_pad = Action.pad(batch_x)
-            batch_y_pad = Action.pad(batch_y)
+
+            batch_x = Action.pad(batch_x)
+            # pad batch_y only if it is a 2-level list
+            if len(batch_y) > 0 and isinstance(batch_y[0], list):
+                batch_y = Action.pad(batch_y)
+
+            # convert list to tensor
+            batch_x = convert_to_torch_tensor(batch_x, use_cuda)
+            batch_y = convert_to_torch_tensor(batch_y, use_cuda)
+
+            # trim data to max_len
+            if max_len is not None and batch_x.size(1) > max_len:
+                batch_x = batch_x[:, :max_len]
+
             if output_length:
                 seq_len = [len(x) for x in batch_x]
-                yield (batch_x_pad, seq_len), batch_y_pad
+                yield (batch_x, seq_len), batch_y
             else:
-                yield batch_x_pad, batch_y_pad
+                yield batch_x, batch_y
 
     @staticmethod
     def pad(batch, fill=0):
@@ -78,6 +93,20 @@ class Action(object):
             model.train()
 
 
+def convert_to_torch_tensor(data_list, use_cuda):
+    """
+    convert lists into (cuda) Tensors
+    :param data_list: 2-level lists
+    :param use_cuda: bool
+    :param reqired_grad: bool
+    :return: PyTorch Tensor of shape [batch_size, max_seq_len]
+    """
+    data_list = torch.Tensor(data_list).long()
+    if torch.cuda.is_available() and use_cuda:
+        data_list = data_list.cuda()
+    return data_list
+
+
 def k_means_1d(x, k, max_iter=100):
     """
     Perform k-means on 1-D data.
diff --git a/fastNLP/core/inference.py b/fastNLP/core/inference.py
index d1d63b78..11a3ba48 100644
--- a/fastNLP/core/inference.py
+++ b/fastNLP/core/inference.py
@@ -2,16 +2,53 @@ import numpy as np
 import torch
 
 from fastNLP.core.action import Batchifier, SequentialSampler
+from fastNLP.core.action import convert_to_torch_tensor
 from fastNLP.loader.preprocess import load_pickle, DEFAULT_UNKNOWN_LABEL
 from fastNLP.modules import utils
 
 
+def make_batch(iterator, data, use_cuda, output_length=False, max_len=None, min_len=None):
+    for indices in iterator:
+        batch_x = [data[idx] for idx in indices]
+        batch_x = pad(batch_x)
+        # convert list to tensor
+        batch_x = convert_to_torch_tensor(batch_x, use_cuda)
+
+        # trim data to max_len
+        if max_len is not None and batch_x.size(1) > max_len:
+            batch_x = batch_x[:, :max_len]
+        if min_len is not None and batch_x.size(1) < min_len:
+            pad_tensor = torch.zeros(batch_x.size(0), min_len - batch_x.size(1)).to(batch_x)
+            batch_x = torch.cat((batch_x, pad_tensor), 1)
+
+        if output_length:
+            seq_len = [len(x) for x in batch_x]
+            yield tuple([batch_x, seq_len])
+        else:
+            yield batch_x
+
+
+def pad(batch, fill=0):
+    """
+    Pad a batch of samples to maximum length.
+    :param batch: list of list
+    :param fill: word index to pad, default 0.
+    :return: a padded batch
+    """
+    max_length = max([len(x) for x in batch])
+    for idx, sample in enumerate(batch):
+        if len(sample) < max_length:
+            batch[idx] = sample + ([fill] * (max_length - len(sample)))
+    return batch
+
+
 class Inference(object):
     """
     This is an interface focusing on predicting output based on trained models.
     It does not care about evaluations of the model, which is different from Tester.
     This is a high-level model wrapper to be called by FastNLP.
     This class does not share any operations with Trainer and Tester.
+    Currently, Inference does not support GPU.
     """
 
     def __init__(self, pickle_path):
@@ -38,10 +75,7 @@ class Inference(object):
 
         iterator = iter(Batchifier(SequentialSampler(data), self.batch_size, drop_last=False))
 
-        num_iter = len(data) // self.batch_size
-
-        for step in range(num_iter):
-            batch_x = self.make_batch(iterator, data)
+        for batch_x in self.make_batch(iterator, data, use_cuda=False):
 
             prediction = self.data_forward(network, batch_x)
 
@@ -54,35 +88,12 @@ class Inference(object):
             network.eval()
         else:
             network.train()
-        self.batch_output.clear()
 
     def data_forward(self, network, x):
         raise NotImplementedError
 
-    @staticmethod
-    def make_batch(iterator, data, output_length=True):
-        indices = next(iterator)
-        batch_x = [data[idx] for idx in indices]
-        batch_x_pad = Inference.pad(batch_x)
-        if output_length:
-            seq_len = [len(x) for x in batch_x]
-            return [batch_x_pad, seq_len]
-        else:
-            return batch_x_pad
-
-    @staticmethod
-    def pad(batch, fill=0):
-        """
-        Pad a batch of samples to maximum length.
-        :param batch: list of list
-        :param fill: word index to pad, default 0.
-        :return: a padded batch
-        """
-        max_length = max([len(x) for x in batch])
-        for idx, sample in enumerate(batch):
-            if len(sample) < max_length:
-                batch[idx] = sample + ([fill] * (max_length - len(sample)))
-        return batch
+    def make_batch(self, iterator, data, use_cuda):
+        raise NotImplementedError
 
     def prepare_input(self, data):
         """
@@ -101,17 +112,8 @@ class Inference(object):
             data_index.append([self.word2index.get(w, default_unknown_index) for w in example])
         return data_index
 
-    def prepare_output(self, batch_outputs):
-        """
-        Transform list of batch outputs into strings.
-        :param batch_outputs: list of 2-D Tensor, of shape [num_batch, batch-size, tag_seq_length].
-        :return:
-        """
-        results = []
-        for batch in batch_outputs:
-            for example in np.array(batch):
-                results.append([self.index2label[int(x)] for x in example])
-        return results
+    def prepare_output(self, data):
+        raise NotImplementedError
 
 
 class SeqLabelInfer(Inference):
@@ -133,10 +135,53 @@ class SeqLabelInfer(Inference):
             raise RuntimeError("[fastnlp] output_length must be true for sequence modeling.")
         # unpack the returned value from make_batch
         x, seq_len = inputs[0], inputs[1]
-        x = torch.Tensor(x).long()
         batch_size, max_len = x.size(0), x.size(1)
         mask = utils.seq_mask(seq_len, max_len)
         mask = mask.byte().view(batch_size, max_len)
         y = network(x)
         prediction = network.prediction(y, mask)
-        return torch.Tensor(prediction)
+        return torch.Tensor(prediction, required_grad=False)
+
+    def make_batch(self, iterator, data, use_cuda):
+        return make_batch(iterator, data, use_cuda, output_length=True)
+
+    def prepare_output(self, batch_outputs):
+        """
+        Transform list of batch outputs into strings.
+        :param batch_outputs: list of 2-D Tensor, of shape [num_batch, batch-size, tag_seq_length].
+        :return:
+        """
+        results = []
+        for batch in batch_outputs:
+            for example in np.array(batch):
+                results.append([self.index2label[int(x)] for x in example])
+        return results
+
+
+class ClassificationInfer(Inference):
+    """
+    Inference on Classification models.
+    """
+
+    def __init__(self, pickle_path):
+        super(ClassificationInfer, self).__init__(pickle_path)
+
+    def data_forward(self, network, x):
+        """Forward through network."""
+        logits = network(x)
+        return logits
+
+    def make_batch(self, iterator, data, use_cuda):
+        return make_batch(iterator, data, use_cuda, output_length=False, min_len=5)
+
+    def prepare_output(self, batch_outputs):
+        """
+        Transform list of batch outputs into strings.
+        :param batch_outputs: list of 2-D Tensor, of shape [num_batch, batch-size, num_classes].
+        :return:
+        """
+        results = []
+        for batch_out in batch_outputs:
+            idx = np.argmax(batch_out.detach().numpy())
+            results.append(self.index2label[idx])
+        return results
diff --git a/fastNLP/core/tester.py b/fastNLP/core/tester.py
index d0208dfd..425f2029 100644
--- a/fastNLP/core/tester.py
+++ b/fastNLP/core/tester.py
@@ -1,5 +1,4 @@
 import _pickle
-import os
 
 import numpy as np
 import torch
@@ -9,15 +8,14 @@ from fastNLP.core.action import RandomSampler, Batchifier
 from fastNLP.modules import utils
 
 
-class BaseTester(Action):
+class BaseTester(object):
     """docstring for Tester"""
 
-    def __init__(self, test_args, action=None):
+    def __init__(self, test_args):
         """
         :param test_args: a dict-like object that has __getitem__ method, can be accessed by "test_args["key_str"]"
         """
         super(BaseTester, self).__init__()
-        self.action = action if action is not None else Action()
         self.validate_in_training = test_args["validate_in_training"]
         self.save_dev_data = None
         self.save_output = test_args["save_output"]
@@ -39,16 +37,23 @@ class BaseTester(Action):
         else:
             self.model = network
 
+        # no backward setting for model
+        for param in network.parameters():
+            param.requires_grad = False
+
         # turn on the testing mode; clean up the history
-        self.action.mode(network, test=True)
+        self.mode(network, test=True)
         self.eval_history.clear()
         self.batch_output.clear()
 
         dev_data = self.prepare_input(self.pickle_path)
 
         iterator = iter(Batchifier(RandomSampler(dev_data), self.batch_size, drop_last=True))
+        n_batches = len(dev_data) // self.batch_size
+        n_print = 1
+        step = 0
 
-        for batch_x, batch_y in self.action.make_batch(iterator, dev_data):
+        for batch_x, batch_y in self.make_batch(iterator, dev_data):
 
             prediction = self.data_forward(network, batch_x)
 
@@ -58,6 +63,7 @@ class BaseTester(Action):
                 self.batch_output.append(prediction)
             if self.save_loss:
                 self.eval_history.append(eval_results)
+            step += 1
 
     def prepare_input(self, data_path):
         """
@@ -70,6 +76,9 @@ class BaseTester(Action):
             self.save_dev_data = data_dev
         return self.save_dev_data
 
+    def mode(self, model, test):
+        Action.mode(model, test)
+
     def data_forward(self, network, x):
         raise NotImplementedError
 
@@ -87,17 +96,20 @@ class BaseTester(Action):
         """
         raise NotImplementedError
 
+    def make_batch(self, iterator, data):
+        raise NotImplementedError
+
 
-class POSTester(BaseTester):
+class SeqLabelTester(BaseTester):
     """
     Tester for sequence labeling.
     """
 
-    def __init__(self, test_args, action=None):
+    def __init__(self, test_args):
         """
         :param test_args: a dict-like object that has __getitem__ method, can be accessed by "test_args["key_str"]"
         """
-        super(POSTester, self).__init__(test_args, action)
+        super(SeqLabelTester, self).__init__(test_args)
         self.max_len = None
         self.mask = None
         self.batch_result = None
@@ -107,13 +119,10 @@ class POSTester(BaseTester):
             raise RuntimeError("[fastnlp] output_length must be true for sequence modeling.")
         # unpack the returned value from make_batch
         x, seq_len = inputs[0], inputs[1]
-        x = torch.Tensor(x).long()
         batch_size, max_len = x.size(0), x.size(1)
         mask = utils.seq_mask(seq_len, max_len)
         mask = mask.byte().view(batch_size, max_len)
-
         if torch.cuda.is_available() and self.use_cuda:
-            x = x.cuda()
             mask = mask.cuda()
         self.mask = mask
 
@@ -121,9 +130,6 @@ class POSTester(BaseTester):
         return y
 
     def evaluate(self, predict, truth):
-        truth = torch.Tensor(truth)
-        if torch.cuda.is_available() and self.use_cuda:
-            truth = truth.cuda()
         batch_size, max_len = predict.size(0), predict.size(1)
         loss = self.model.loss(predict, truth, self.mask) / batch_size
 
@@ -147,8 +153,11 @@ class POSTester(BaseTester):
         loss, accuracy = self.metrics()
         return "dev loss={:.2f}, accuracy={:.2f}".format(loss, accuracy)
 
+    def make_batch(self, iterator, data):
+        return Action.make_batch(iterator, data, use_cuda=self.use_cuda, output_length=True)
+
 
-class ClassTester(BaseTester):
+class ClassificationTester(BaseTester):
     """Tester for classification."""
 
     def __init__(self, test_args):
@@ -156,7 +165,7 @@ class ClassTester(BaseTester):
         :param test_args: a dict-like object that has __getitem__ method, \
             can be accessed by "test_args["key_str"]"
         """
-        # super(ClassTester, self).__init__()
+        super(ClassificationTester, self).__init__(test_args)
         self.pickle_path = test_args["pickle_path"]
 
         self.save_dev_data = None
@@ -164,111 +173,8 @@ class ClassTester(BaseTester):
         self.mean_loss = None
         self.iterator = None
 
-        if "test_name" in test_args:
-            self.test_name = test_args["test_name"]
-        else:
-            self.test_name = "data_test.pkl"
-
-        if "validate_in_training" in test_args:
-            self.validate_in_training = test_args["validate_in_training"]
-        else:
-            self.validate_in_training = False
-
-        if "save_output" in test_args:
-            self.save_output = test_args["save_output"]
-        else:
-            self.save_output = False
-
-        if "save_loss" in test_args:
-            self.save_loss = test_args["save_loss"]
-        else:
-            self.save_loss = True
-
-        if "batch_size" in test_args:
-            self.batch_size = test_args["batch_size"]
-        else:
-            self.batch_size = 50
-        if "use_cuda" in test_args:
-            self.use_cuda = test_args["use_cuda"]
-        else:
-            self.use_cuda = True
-
-        if "max_len" in test_args:
-            self.max_len = test_args["max_len"]
-        else:
-            self.max_len = None
-
-        self.model = None
-        self.eval_history = []
-        self.batch_output = []
-
-    def test(self, network):
-        # prepare model
-        if torch.cuda.is_available() and self.use_cuda:
-            self.model = network.cuda()
-        else:
-            self.model = network
-
-        # no backward setting for model
-        for param in self.model.parameters():
-            param.requires_grad = False
-
-        # turn on the testing mode; clean up the history
-        self.mode(network, test=True)
-
-        # prepare test data
-        data_test = self.prepare_input(self.pickle_path, self.test_name)
-
-        # data generator
-        self.iterator = iter(Batchifier(
-            RandomSampler(data_test), self.batch_size, drop_last=False))
-
-        # test
-        n_batches = len(data_test) // self.batch_size
-        n_print = n_batches // 10
-        step = 0
-        for batch_x, batch_y in self.make_batch(data_test, max_len=self.max_len):
-            prediction = self.data_forward(network, batch_x)
-            eval_results = self.evaluate(prediction, batch_y)
-
-            if self.save_output:
-                self.batch_output.append(prediction)
-            if self.save_loss:
-                self.eval_history.append(eval_results)
-
-            if step % n_print == 0:
-                print("step: {:>5}".format(step))
-
-            step += 1
-
-    def prepare_input(self, data_dir, file_name):
-        """Prepare data."""
-        file_path = os.path.join(data_dir, file_name)
-        with open(file_path, 'rb') as f:
-            data = _pickle.load(f)
-        return data
-
-    def make_batch(self, data, max_len=None):
-        """Batch and pad data."""
-        for indices in self.iterator:
-            # generate batch and pad
-            batch = [data[idx] for idx in indices]
-            batch_x = [sample[0] for sample in batch]
-            batch_y = [sample[1] for sample in batch]
-            batch_x = self.pad(batch_x)
-
-            # convert to tensor
-            batch_x = torch.tensor(batch_x, dtype=torch.long)
-            batch_y = torch.tensor(batch_y, dtype=torch.long)
-            if torch.cuda.is_available() and self.use_cuda:
-                batch_x = batch_x.cuda()
-                batch_y = batch_y.cuda()
-
-            # trim data to max_len
-            if max_len is not None and batch_x.size(1) > max_len:
-                batch_x = batch_x[:, :max_len]
-
-            yield batch_x, batch_y
+    def make_batch(self, iterator, data, max_len=None):
+        return Action.make_batch(iterator, data, use_cuda=self.use_cuda, max_len=max_len)
 
     def data_forward(self, network, x):
         """Forward through network."""
@@ -289,10 +195,3 @@ class ClassTester(BaseTester):
         acc = float(torch.sum(y_pred == y_true)) / len(y_true)
         return y_true.cpu().numpy(), y_prob.cpu().numpy(), acc
 
-    def mode(self, model, test=True):
-        """TODO: combine this function with Trainer ?? """
-        if test:
-            model.eval()
-        else:
-            model.train()
-        self.eval_history.clear()
diff --git a/fastNLP/core/trainer.py b/fastNLP/core/trainer.py
index 7024029f..d7515a40 100644
--- a/fastNLP/core/trainer.py
+++ b/fastNLP/core/trainer.py
@@ -9,12 +9,12 @@ import torch.nn as nn
 
 from fastNLP.core.action import Action
 from fastNLP.core.action import RandomSampler, Batchifier
-from fastNLP.core.tester import POSTester
+from fastNLP.core.tester import SeqLabelTester, ClassificationTester
 from fastNLP.modules import utils
 from fastNLP.saver.model_saver import ModelSaver
 
 
-class BaseTrainer(Action):
+class BaseTrainer(object):
     """Base trainer for all trainers.
         Trainer receives a model and data, and then performs training.
 
@@ -24,10 +24,9 @@ class BaseTrainer(Action):
         - get_loss
     """
 
-    def __init__(self, train_args, action=None):
+    def __init__(self, train_args):
         """
         :param train_args: dict of (key, value), or dict-like object. key is str.
-        :param action: (optional) an Action object that wrap most operations shared by Trainer, Tester, and Inference.
 
         The base trainer requires the following keys:
         - epochs: int, the number of epochs in training
@@ -36,7 +35,6 @@ class BaseTrainer(Action):
         - pickle_path: str, the path to pickle files for pre-processing
         """
         super(BaseTrainer, self).__init__()
-        self.action = action if action is not None else Action()
         self.n_epochs = train_args["epochs"]
         self.batch_size = train_args["batch_size"]
         self.pickle_path = train_args["pickle_path"]
@@ -79,7 +77,7 @@ class BaseTrainer(Action):
             default_valid_args = {"save_output": True, "validate_in_training": True, "save_dev_input": True,
                                   "save_loss": True, "batch_size": self.batch_size, "pickle_path": self.pickle_path,
                                   "use_cuda": self.use_cuda}
-            validator = POSTester(default_valid_args, self.action)
+            validator = self._create_validator(default_valid_args)
 
         self.define_optimizer()
 
@@ -92,12 +90,12 @@ class BaseTrainer(Action):
         for epoch in range(1, self.n_epochs + 1):
 
             # turn on network training mode; prepare batch iterator
-            self.action.mode(network, test=False)
+            self.mode(network, test=False)
             iterator = iter(Batchifier(RandomSampler(data_train), self.batch_size, drop_last=False))
 
             # training iterations in one epoch
             step = 0
-            for batch_x, batch_y in self.action.make_batch(iterator, data_train, output_length=True):
+            for batch_x, batch_y in self.make_batch(iterator, data_train):
 
                 prediction = self.data_forward(network, batch_x)
 
@@ -142,6 +140,12 @@ class BaseTrainer(Action):
             files.append(data)
         return tuple(files)
 
+    def make_batch(self, iterator, data):
+        raise NotImplementedError
+
+    def mode(self, network, test):
+        Action.mode(network, test)
+
     def define_optimizer(self):
         """
         Define framework-specific optimizer specified by the models.
@@ -203,6 +207,9 @@ class BaseTrainer(Action):
         """
         ModelSaver(self.model_saved_path + "model_best_dev.pkl").save_pytorch(network)
 
+    def _create_validator(self, valid_args):
+        raise NotImplementedError
+
 
 class ToyTrainer(BaseTrainer):
     """
@@ -217,12 +224,6 @@ class ToyTrainer(BaseTrainer):
         data_dev = _pickle.load(open(data_path + "/data_train.pkl", "rb"))
         return data_train, data_dev, 0, 1
 
-    def mode(self, test=False):
-        if test:
-            self.model.eval()
-        else:
-            self.model.train()
-
     def data_forward(self, network, x):
         return network(x)
 
@@ -246,8 +247,8 @@ class SeqLabelTrainer(BaseTrainer):
 
     """
 
-    def __init__(self, train_args, action=None):
-        super(SeqLabelTrainer, self).__init__(train_args, action)
+    def __init__(self, train_args):
+        super(SeqLabelTrainer, self).__init__(train_args)
         self.vocab_size = train_args["vocab_size"]
         self.num_classes = train_args["num_classes"]
         self.max_len = None
@@ -269,14 +270,12 @@ class SeqLabelTrainer(BaseTrainer):
             raise RuntimeError("[fastnlp] output_length must be true for sequence modeling.")
         # unpack the returned value from make_batch
         x, seq_len = inputs[0], inputs[1]
-        x = torch.Tensor(x).long()
 
         batch_size, max_len = x.size(0), x.size(1)
         mask = utils.seq_mask(seq_len, max_len)
         mask = mask.byte().view(batch_size, max_len)
 
         if torch.cuda.is_available() and self.use_cuda:
-            x = x.cuda()
             mask = mask.cuda()
         self.mask = mask
 
@@ -290,9 +289,6 @@ class SeqLabelTrainer(BaseTrainer):
         :param truth: ground truth label vector, [batch_size, max_len]
         :return: a scalar
         """
-        truth = torch.Tensor(truth)
-        if torch.cuda.is_available() and self.use_cuda:
-            truth = truth.cuda()
         batch_size, max_len = predict.size(0), predict.size(1)
         assert truth.shape == (batch_size, max_len)
 
@@ -307,32 +303,18 @@ class SeqLabelTrainer(BaseTrainer):
         else:
             return False
 
+    def make_batch(self, iterator, data):
+        return Action.make_batch(iterator, data, output_length=True, use_cuda=self.use_cuda)
 
-class LanguageModelTrainer(BaseTrainer):
-    """
-    Trainer for Language Model
-    """
-
-    def __init__(self, train_args):
-        super(LanguageModelTrainer, self).__init__(train_args)
-
-    def prepare_input(self, data_path):
-        pass
+    def _create_validator(self, valid_args):
+        return SeqLabelTester(valid_args)
 
 
-class ClassTrainer(BaseTrainer):
+class ClassificationTrainer(BaseTrainer):
     """Trainer for classification."""
 
-    def __init__(self, train_args, action=None):
-        super(ClassTrainer, self).__init__(train_args, action)
-        self.n_epochs = train_args["epochs"]
-        self.batch_size = train_args["batch_size"]
-        self.pickle_path = train_args["pickle_path"]
-
-        if "validate" in train_args:
-            self.validate = train_args["validate"]
-        else:
-            self.validate = False
+    def __init__(self, train_args):
+        super(ClassificationTrainer, self).__init__(train_args)
         if "learn_rate" in train_args:
             self.learn_rate = train_args["learn_rate"]
         else:
@@ -341,15 +323,11 @@ class ClassTrainer(BaseTrainer):
             self.momentum = train_args["momentum"]
         else:
             self.momentum = 0.9
-        if "use_cuda" in train_args:
-            self.use_cuda = train_args["use_cuda"]
-        else:
-            self.use_cuda = True
 
-        self.model = None
         self.iterator = None
         self.loss_func = None
         self.optimizer = None
+        self.best_accuracy = 0
 
     def define_loss(self):
         self.loss_func = nn.CrossEntropyLoss()
@@ -365,9 +343,6 @@ class ClassTrainer(BaseTrainer):
 
     def data_forward(self, network, x):
         """Forward through network."""
-        x = torch.Tensor(x).long()
-        if torch.cuda.is_available() and self.use_cuda:
-            x = x.cuda()
         logits = network(x)
         return logits
 
@@ -380,31 +355,21 @@ class ClassTrainer(BaseTrainer):
         """Apply gradient."""
         self.optimizer.step()
 
-    """
-    def make_batch(self, data):
-        for indices in self.iterator:
-            batch = [data[idx] for idx in indices]
-            batch_x = [sample[0] for sample in batch]
-            batch_y = [sample[1] for sample in batch]
-            batch_x = self.pad(batch_x)
-
-            batch_x = torch.Tensor(batch_x).long()
-            batch_y = torch.Tensor(batch_y).long()
-            if torch.cuda.is_available() and self.use_cuda:
-                batch_x = batch_x.cuda()
-                batch_y = batch_y.cuda()
-
-            yield batch_x, batch_y
-    """
+    def make_batch(self, iterator, data):
+        return Action.make_batch(iterator, data, output_length=False, use_cuda=self.use_cuda)
 
     def get_acc(self, y_logit, y_true):
         """Compute accuracy."""
         y_pred = torch.argmax(y_logit, dim=-1)
         return int(torch.sum(y_true == y_pred)) / len(y_true)
 
+    def best_eval_result(self, validator):
+        _, _, accuracy = validator.metrics()
+        if accuracy > self.best_accuracy:
+            self.best_accuracy = accuracy
+            return True
+        else:
+            return False
 
-if __name__ == "__name__":
-    train_args = {"epochs": 1, "validate": False, "batch_size": 3, "pickle_path": "./"}
-    trainer = BaseTrainer(train_args)
-    data_train = [[[1, 2, 3, 4], [0]] * 10] + [[[1, 3, 5, 2], [1]] * 10]
-    trainer.make_batch(data=data_train)
+    def _create_validator(self, valid_args):
+        return ClassificationTester(valid_args)
diff --git a/fastNLP/models/cnn_text_classification.py b/fastNLP/models/cnn_text_classification.py
index 76a6cd97..66bb5ecc 100644
--- a/fastNLP/models/cnn_text_classification.py
+++ b/fastNLP/models/cnn_text_classification.py
@@ -1,13 +1,14 @@
 # python: 3.6
 # encoding: utf-8
 
+import torch
 import torch.nn as nn
+
 # import torch.nn.functional as F
-from fastNLP.models.base_model import BaseModel
 from fastNLP.modules.encoder.conv_maxpool import ConvMaxpool
 
 
-class CNNText(BaseModel):
+class CNNText(torch.nn.Module):
     """
     Text classification model by character CNN, the implementation of paper
     'Yoon Kim. 2014. Convolution Neural Networks for Sentence
diff --git a/reproduction/chinese_word_seg/cws_train.py b/reproduction/chinese_word_seg/cws_train.py
index 3378a8a5..0a235be0 100644
--- a/reproduction/chinese_word_seg/cws_train.py
+++ b/reproduction/chinese_word_seg/cws_train.py
@@ -8,7 +8,7 @@ from fastNLP.loader.dataset_loader import TokenizeDatasetLoader, BaseLoader
 from fastNLP.loader.preprocess import POSPreprocess, load_pickle
 from fastNLP.saver.model_saver import ModelSaver
 from fastNLP.loader.model_loader import ModelLoader
-from fastNLP.core.tester import POSTester
+from fastNLP.core.tester import SeqLabelTester
 from fastNLP.models.sequence_modeling import SeqLabeling
 from fastNLP.core.inference import Inference
 
@@ -96,7 +96,7 @@ def test():
     ConfigLoader("config.cfg", "").load_config("./data_for_tests/config", {"POS_test": test_args})
 
     # Tester
-    tester = POSTester(test_args)
+    tester = SeqLabelTester(test_args)
 
     # Start testing
     tester.test(model)
diff --git a/test/seq_labeling.py b/test/seq_labeling.py
index 904720ca..db171215 100644
--- a/test/seq_labeling.py
+++ b/test/seq_labeling.py
@@ -8,7 +8,7 @@ from fastNLP.loader.dataset_loader import POSDatasetLoader, BaseLoader
 from fastNLP.loader.preprocess import POSPreprocess, load_pickle
 from fastNLP.saver.model_saver import ModelSaver
 from fastNLP.loader.model_loader import ModelLoader
-from fastNLP.core.tester import POSTester
+from fastNLP.core.tester import SeqLabelTester
 from fastNLP.models.sequence_modeling import SeqLabeling
 from fastNLP.core.inference import SeqLabelInfer
 
@@ -101,7 +101,7 @@ def train_and_test():
     ConfigLoader("config.cfg", "").load_config("./data_for_tests/config", {"POS_test": test_args})
 
     # Tester
-    tester = POSTester(test_args)
+    tester = SeqLabelTester(test_args)
 
     # Start testing
     tester.test(model)
@@ -112,5 +112,5 @@ def train_and_test():
 
 
 if __name__ == "__main__":
-    train_and_test()
+    # train_and_test()
     infer()
diff --git a/test/test_cws.py b/test/test_cws.py
index 5d0dc3c2..f293aefd 100644
--- a/test/test_cws.py
+++ b/test/test_cws.py
@@ -8,7 +8,7 @@ from fastNLP.loader.dataset_loader import TokenizeDatasetLoader, BaseLoader
 from fastNLP.loader.preprocess import POSPreprocess, load_pickle
 from fastNLP.saver.model_saver import ModelSaver
 from fastNLP.loader.model_loader import ModelLoader
-from fastNLP.core.tester import POSTester
+from fastNLP.core.tester import SeqLabelTester
 from fastNLP.models.sequence_modeling import SeqLabeling
 from fastNLP.core.inference import Inference
 
@@ -101,7 +101,7 @@ def train_test():
     ConfigLoader("config.cfg", "").load_config("./data_for_tests/config", {"POS_test": test_args})
 
     # Tester
-    tester = POSTester(test_args)
+    tester = SeqLabelTester(test_args)
 
     # Start testing
     tester.test(model)
diff --git a/test/test_tester.py b/test/test_tester.py
index dd1e6c23..9a3d949e 100644
--- a/test/test_tester.py
+++ b/test/test_tester.py
@@ -1,4 +1,4 @@
-from fastNLP.core.tester import POSTester
+from fastNLP.core.tester import SeqLabelTester
 from fastNLP.loader.config_loader import ConfigSection, ConfigLoader
 from fastNLP.loader.dataset_loader import TokenizeDatasetLoader
 from fastNLP.loader.preprocess import POSPreprocess
@@ -26,7 +26,7 @@ def foo():
     valid_args = {"save_output": True, "validate_in_training": True, "save_dev_input": True,
                   "save_loss": True, "batch_size": 8, "pickle_path": "./data_for_tests/",
                   "use_cuda": True}
-    validator = POSTester(valid_args)
+    validator = SeqLabelTester(valid_args)
 
     print("start validation.")
     validator.test(model)
diff --git a/test/text_classify.py b/test/text_classify.py
index 88d11b02..f18d4a38 100644
--- a/test/text_classify.py
+++ b/test/text_classify.py
@@ -3,16 +3,45 @@
 
 import os
 
-from fastNLP.core.trainer import ClassTrainer
+from fastNLP.core.inference import ClassificationInfer
+from fastNLP.core.trainer import ClassificationTrainer
 from fastNLP.loader.dataset_loader import ClassDatasetLoader
+from fastNLP.loader.model_loader import ModelLoader
 from fastNLP.loader.preprocess import ClassPreprocess
 from fastNLP.models.cnn_text_classification import CNNText
+from fastNLP.saver.model_saver import ModelSaver
 
-if __name__ == "__main__":
-    data_dir = "./data_for_tests/"
-    train_file = 'text_classify.txt'
-    model_name = "model_class.pkl"
+data_dir = "./data_for_tests/"
+train_file = 'text_classify.txt'
+model_name = "model_class.pkl"
+
+
+def infer():
+    # load dataset
+    print("Loading data...")
+    ds_loader = ClassDatasetLoader("train", os.path.join(data_dir, train_file))
+    data = ds_loader.load()
+    unlabeled_data = [x[0] for x in data]
+
+    # pre-process data
+    pre = ClassPreprocess(data_dir)
+    vocab_size, n_classes = pre.process(data, "data_train.pkl")
+    print("vocabulary size:", vocab_size)
+    print("number of classes:", n_classes)
+
+    # construct model
+    print("Building model...")
+    cnn = CNNText(class_num=n_classes, embed_num=vocab_size)
+    # Dump trained parameters into the model
+    ModelLoader.load_pytorch(cnn, "./data_for_tests/saved_model.pkl")
+    print("model loaded!")
+
+    infer = ClassificationInfer(data_dir)
+    results = infer.predict(cnn, unlabeled_data)
+    print(results)
 
+
+def train():
     # load dataset
     print("Loading data...")
     ds_loader = ClassDatasetLoader("train", os.path.join(data_dir, train_file))
@@ -40,5 +69,16 @@ if __name__ == "__main__":
         "model_saved_path": "./data_for_tests/",
         "use_cuda": True
     }
-    trainer = ClassTrainer(train_args)
+    trainer = ClassificationTrainer(train_args)
     trainer.train(cnn)
+
+    print("Training finished!")
+
+    saver = ModelSaver("./data_for_tests/saved_model.pkl")
+    saver.save_pytorch(cnn)
+    print("Model saved!")
+
+
+if __name__ == "__main__":
+    # train()
+    infer()