diff --git a/python/paddle/fluid/tests/unittests/test_decoupled_py_reader.py b/python/paddle/fluid/tests/unittests/test_decoupled_py_reader.py
index 0fbf0d42f5dcc34947235d9bd1db6f8b1c07d59a..a16f21c0f97c0902dd6c26561ed3f707b28ff947 100644
--- a/python/paddle/fluid/tests/unittests/test_decoupled_py_reader.py
+++ b/python/paddle/fluid/tests/unittests/test_decoupled_py_reader.py
@@ -21,12 +21,13 @@ import unittest
 
 EPOCH_NUM = 20
 BATCH_SIZE = 32
+BATCH_NUM = 20
 CLASS_NUM = 10
 
 
 def random_reader():
     np.random.seed(1)
-    for i in range(BATCH_SIZE * 40):
+    for i in range(BATCH_SIZE * BATCH_NUM):
         image = np.random.random([784])
         label = np.random.random_integers(low=0, high=CLASS_NUM - 1)
         yield image, label