diff --git a/audio_data_utils.py b/audio_data_utils.py
index abb7f1e9931543349c93d9310d48638b5baf74af..692a42809f790845e8d3349ccce786d9fddce8cd 100644
--- a/audio_data_utils.py
+++ b/audio_data_utils.py
@@ -247,22 +247,25 @@ class DataGenerator(object):
             new_batch.append((padded_audio, text))
         return new_batch
 
-    def __batch_shuffle__(self, manifest, batch_size):
+    def __batch_shuffle__(self, manifest, batch_shuffle_size):
         """
         1. Sort the audio clips by duration.
-        2. Generate a random number `k`, k in [0, batch_size).
+        2. Generate a random number `k`, k in [0, batch_shuffle_size).
         3. Randomly remove `k` instances in order to make different mini-batches,
-           then make minibatches and each minibatch size is batch_size.
+           then make minibatches and each minibatch size is batch_shuffle_size.
         4. Shuffle the minibatches.
 
         :param manifest: manifest file.
         :type manifest: list
-        :param batch_size: batch size.
-        :type batch_size: int
+        :param batch_shuffle_size: This size is uesed to generate a random number,
+                                   it usually equals to batch size.
+        :type batch_shuffle_size: int
+        :return: batch shuffled mainifest.
+        :rtype: list
         """
         manifest.sort(key=lambda x: x["duration"])
-        shift_len = self.__random__.randint(0, batch_size - 1)
-        batch_manifest = zip(*[iter(manifest[shift_len:])] * batch_size)
+        shift_len = self.__random__.randint(0, batch_shuffle_size - 1)
+        batch_manifest = zip(*[iter(manifest[shift_len:])] * batch_shuffle_size)
         self.__random__.shuffle(batch_manifest)
         batch_manifest = list(sum(batch_manifest, ()))
         res_len = len(manifest) - shift_len - len(batch_manifest)
@@ -270,11 +273,7 @@ class DataGenerator(object):
         batch_manifest.extend(manifest[0:shift_len])
         return batch_manifest
 
-    def instance_reader_creator(self,
-                                manifest_path,
-                                batch_size,
-                                sortagrad=True,
-                                shuffle=False):
+    def instance_reader_creator(self, manifest):
         """
         Instance reader creator for audio data. Creat a callable function to
         produce instances of data.
@@ -282,35 +281,19 @@ class DataGenerator(object):
         Instance: a tuple of a numpy ndarray of audio spectrogram and a list of
         tokenized and indexed transcription text.
 
-        :param manifest_path: Filepath of manifest for audio clip files.
-        :type manifest_path: basestring
-        :param sortagrad: Sort the audio clips by duration in the first epoc
-                          if set True.
-        :type sortagrad: bool
-        :param shuffle: Shuffle the audio clips if set True.
-        :type shuffle: bool
+        :param manifest: Filepath of manifest for audio clip files.
+        :type manifest: basestring
         :return: Data reader function.
         :rtype: callable
         """
 
         def reader():
-            # read manifest
-            manifest = self.__read_manifest__(
-                manifest_path=manifest_path,
-                max_duration=self.__max_duration__,
-                min_duration=self.__min_duration__)
-            # sort (by duration) or shuffle manifest
-            if self.__epoc__ == 0 and sortagrad:
-                manifest.sort(key=lambda x: x["duration"])
-            elif shuffle:
-                manifest = self.__batch_shuffle__(manifest, batch_size)
             # extract spectrogram feature
             for instance in manifest:
                 spectrogram = self.__audio_featurize__(
                     instance["audio_filepath"])
                 transcript = self.__text_featurize__(instance["text"])
                 yield (spectrogram, transcript)
-            self.__epoc__ += 1
 
         return reader
 
@@ -320,7 +303,7 @@ class DataGenerator(object):
                              padding_to=-1,
                              flatten=False,
                              sortagrad=False,
-                             shuffle=False):
+                             batch_shuffle=False):
         """
         Batch data reader creator for audio data. Creat a callable function to
         produce batches of data.
@@ -343,18 +326,28 @@ class DataGenerator(object):
         :param sortagrad: Sort the audio clips by duration in the first epoc
                           if set True.
         :type sortagrad: bool
-        :param shuffle: Shuffle the audio clips if set True.
-        :type shuffle: bool
+        :param batch_shuffle: Shuffle the audio clips if set True. It is
+                              not a thorough instance-wise shuffle,
+                              but a specific batch-wise shuffle.
+        :type batch_shuffle: bool
         :return: Batch reader function, producing batches of data when called.
         :rtype: callable
         """
 
         def batch_reader():
-            instance_reader = self.instance_reader_creator(
+            # read manifest
+            manifest = self.__read_manifest__(
                 manifest_path=manifest_path,
-                batch_size=batch_size,
-                sortagrad=sortagrad,
-                shuffle=shuffle)
+                max_duration=self.__max_duration__,
+                min_duration=self.__min_duration__)
+
+            # sort (by duration) or shuffle manifest
+            if self.__epoc__ == 0 and sortagrad:
+                manifest.sort(key=lambda x: x["duration"])
+            elif batch_shuffle:
+                manifest = self.__batch_shuffle__(manifest, batch_size)
+
+            instance_reader = self.instance_reader_creator(manifest)
             batch = []
             for instance in instance_reader():
                 batch.append(instance)
@@ -363,6 +356,7 @@ class DataGenerator(object):
                     batch = []
             if len(batch) > 0:
                 yield self.__padding_batch__(batch, padding_to, flatten)
+            self.__epoc__ += 1
 
         return batch_reader