diff --git a/python/paddle/fluid/dygraph/layers.py b/python/paddle/fluid/dygraph/layers.py
index b9a43cbbe1afcf32b6319ada384b0d685fdc60e3..b157ce81d82fc7f6d2231fc22a5246b65de31035 100644
--- a/python/paddle/fluid/dygraph/layers.py
+++ b/python/paddle/fluid/dygraph/layers.py
@@ -959,7 +959,7 @@ class Layer(core.Layer):
                 for prefix, layer in model.named_sublayers():
                     print(prefix, layer)
         """
-        assert isinstance(sublayer, core.Layer)
+        assert (isinstance(sublayer, core.Layer) or sublayer == None)
 
         self._sub_layers[name] = sublayer
         return sublayer