diff --git a/mindspore/train/model.py b/mindspore/train/model.py
index a8f142c9dd..adf7495eb8 100755
--- a/mindspore/train/model.py
+++ b/mindspore/train/model.py
@@ -549,6 +549,8 @@ class Model:
             >>> model.train(2, dataset)
         """
         check_bool(dataset_sink_mode)
+        if sink_size == -1:
+            sink_size = train_dataset.get_dataset_size()
         check_int(sink_size)
         if sink_size < -1 or sink_size == 0:
             raise ValueError("The sink_size must be -1 or positive, but got sink_size {}.".format(sink_size))
diff --git a/tests/dataset_mock.py b/tests/dataset_mock.py
index ad6fd0f12c..988f15dd8c 100644
--- a/tests/dataset_mock.py
+++ b/tests/dataset_mock.py
@@ -21,7 +21,7 @@ from mindspore import Tensor
 class MindData:
     """ Stub for MindData """
 
-    def __init__(self, size=None, batch_size=None, repeat_count=1,
+    def __init__(self, size=1, batch_size=None, repeat_count=1,
                  np_types=None, output_shapes=None, input_indexs=()):
         self._size = size
         self._batch_size = batch_size
diff --git a/tests/ut/python/parallel/test_loss_scale.py b/tests/ut/python/parallel/test_loss_scale.py
index 88997160f8..9649679474 100644
--- a/tests/ut/python/parallel/test_loss_scale.py
+++ b/tests/ut/python/parallel/test_loss_scale.py
@@ -113,7 +113,7 @@ class TrainOneStepWithLossScaleCell(nn.Cell):
 
 class DatasetLenet(MindData):
     def __init__(self, predict, label, length=3):
-        super(DatasetLenet, self).__init__()
+        super(DatasetLenet, self).__init__(size=length)
         self.predict = predict
         self.label = label
         self.index = 0