diff --git a/python/paddle/optimizer/lr.py b/python/paddle/optimizer/lr.py
index 528fab1c2b98dc419bc3e76fe84b49e95b947f6b..d0d5eef03c42c032c7593998aeccae65ca5767fc 100644
--- a/python/paddle/optimizer/lr.py
+++ b/python/paddle/optimizer/lr.py
@@ -1360,6 +1360,8 @@ class ReduceOnPlateau(LRScheduler):
         if not _in_legacy_dygraph():
             tmp = core.eager.Tensor
         else:
+            # need to declarate explicitly
+            from paddle.framework import VarBase as Tensor
             tmp = Tensor
         # loss must be float, numpy.ndarray or 1-D Tensor with shape [1]
         if isinstance(metrics, (tmp, numpy.ndarray)):