diff --git a/python/paddle/v2/parameters.py b/python/paddle/v2/parameters.py
index d686d09f220671fce50be0784e354f97cb109f32..64805d0c504b876f4d1f6657fe94457534a0b278 100644
--- a/python/paddle/v2/parameters.py
+++ b/python/paddle/v2/parameters.py
@@ -249,7 +249,7 @@ class Parameters(object):
         size = reduce(lambda a, b: a * b, param.shape)
         f.write(struct.pack("IIQ", 0, 4, size))
         param = param.astype(np.float32)
-        f.write(param.tobytes())
+        f.write(param.tostring())
 
     def deserialize(self, name, f):
         """