diff --git a/mindspore/dataset/engine/samplers.py b/mindspore/dataset/engine/samplers.py
index 56ef705f60..e91dca9ce0 100644
--- a/mindspore/dataset/engine/samplers.py
+++ b/mindspore/dataset/engine/samplers.py
@@ -115,6 +115,8 @@ class Sampler:
         return self.child_sampler.is_sharded()
 
     def get_num_samples(self):
+        if self.num_samples is None:
+            return None
         return self._get_indices().size