diff --git a/python/paddle/trainer_config_helpers/layers.py b/python/paddle/trainer_config_helpers/layers.py
index aae419566f051e894f25e83902099ee0f39a469c..a89b7eb0c91973879839f0e7c955db1413bbf1d8 100755
--- a/python/paddle/trainer_config_helpers/layers.py
+++ b/python/paddle/trainer_config_helpers/layers.py
@@ -4873,7 +4873,7 @@ def nce_layer(input,
     if neg_distribution is not None:
         assert isinstance(neg_distribution, collections.Sequence)
         assert len(neg_distribution) == num_classes
-        assert sum(neg_distribution) == 1
+        assert abs(sum(neg_distribution) - 1.0) < 1e-5
     if not isinstance(act, BaseActivation):
         raise TypeError()