diff --git a/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_fit_a_line.py b/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_fit_a_line.py
index 7ad5e2c594f24999e298533b6c05ba688a935f0b..045db8390cd52689a2a803c3387c90776a44ee73 100644
--- a/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_fit_a_line.py
+++ b/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_fit_a_line.py
@@ -15,6 +15,8 @@
 import numpy as np
 import paddle.v2 as paddle
 import paddle.v2.fluid as fluid
+import math
+import sys
 
 # need to fix random seed and training data to compare the loss
 # value accurately calculated by the default and the memory optimization
@@ -63,4 +65,6 @@ for pass_id in range(PASS_NUM):
 
         if avg_loss_value[0] < 10.0:
             exit(0)  # if avg cost less than 10.0, we think our code is good.
+        if math.isnan(float(avg_loss_value)):
+            sys.exit("got NaN loss, training failed.")
 exit(1)
diff --git a/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_image_classification_train.py b/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_image_classification_train.py
index 26673afd83c48328c3f354e82bfa3725aa4805b5..9fbb36d3638bd537020247d6f762afd4ed5d402f 100644
--- a/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_image_classification_train.py
+++ b/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_image_classification_train.py
@@ -18,6 +18,8 @@ import sys
 
 import paddle.v2 as paddle
 import paddle.v2.fluid as fluid
+import math
+import sys
 
 # need to fix random seed and training data to compare the loss
 # value accurately calculated by the default and the memory optimization
@@ -152,7 +154,10 @@ for pass_id in range(PASS_NUM):
         print("loss:" + str(loss) + " acc:" + str(acc) + " pass_acc:" + str(
             pass_acc))
         # this model is slow, so if we can train two mini batch, we think it works properly.
+
         if i > 2:
             exit(0)
+        if math.isnan(float(loss)):
+            sys.exit("got NaN loss, training failed.")
         i += 1
 exit(1)
diff --git a/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_machine_translation.py b/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_machine_translation.py
index ffd53e7a78142162317a677de49c1821635a65b5..48abaa8d87563b7132c5d8962bc33283a104e67a 100644
--- a/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_machine_translation.py
+++ b/python/paddle/v2/fluid/tests/book_memory_optimization/test_memopt_machine_translation.py
@@ -19,6 +19,8 @@ import paddle.v2.fluid.core as core
 import paddle.v2.fluid.framework as framework
 import paddle.v2.fluid.layers as layers
 from paddle.v2.fluid.executor import Executor
+import math
+import sys
 
 dict_size = 30000
 source_dict_dim = target_dict_dim = dict_size
@@ -137,6 +139,8 @@ def main():
                   " avg_cost=" + str(avg_cost_val))
             if batch_id > 2:
                 exit(0)
+            if math.isnan(float(avg_cost_val)):
+                sys.exit("got NaN loss, training failed.")
             batch_id += 1