diff --git a/python/paddle/v2/framework/tests/mnist.py b/python/paddle/v2/framework/tests/mnist.py
index eefd5709a3bd7a34c3aaec370690158372562328..e878bfa4e9b2be7ff356e1e3861da2afc56063d7 100644
--- a/python/paddle/v2/framework/tests/mnist.py
+++ b/python/paddle/v2/framework/tests/mnist.py
@@ -205,7 +205,8 @@ train_reader = paddle.batch(
 
 
 def test(cost_name):
-    test_reader = paddle.batch(paddle.dataset.mnist.test(), batch_size=128)
+    test_reader = paddle.batch(
+        paddle.dataset.mnist.test(), batch_size=BATCH_SIZE)
     cost = []
     error = []
     for data in test_reader():