diff --git a/fastNLP/core/samplers/reproducible_batch_sampler.py b/fastNLP/core/samplers/reproducible_batch_sampler.py
index be43bc74..171a784b 100644
--- a/fastNLP/core/samplers/reproducible_batch_sampler.py
+++ b/fastNLP/core/samplers/reproducible_batch_sampler.py
@@ -19,7 +19,7 @@ from abc import abstractmethod
 
 class ReproducibleBatchSampler:
     def __init__(self, **kwargs):
-        pass
+        self.num_replicas = 1
 
     @abstractmethod
     def set_distributed(self, num_replicas, rank, pad=True):
@@ -53,14 +53,6 @@ class ReproducibleBatchSampler:
     def batch_idx_in_epoch(self):
         raise NotImplementedError("Each specific batch_sampler should implement its own `batch_idx_in_epoch` property.")
 
-    @property
-    def num_replicas(self):
-        return self._num_replicas
-
-    @num_replicas.setter
-    def num_replicas(self, value):
-        self._num_replicas = value
-
 
 class RandomBatchSampler(ReproducibleBatchSampler):
     # 这两个参数的值应当交给 driver 的 get_dataloader_args 函数去拿；
@@ -322,7 +314,7 @@ class BucketedBatchSampler(ReproducibleBatchSampler):
             if len(batches[-1])==0:
                 batches.pop(-1)
 
-        assert len(list(chain(*batches))) == self.num_left_samples
+        assert sum(map(len, batches)) == self.num_left_samples
 
         if self.drop_last and len(batches) >= 1 and len(batches[-1]) < self.batch_size:
             batches = batches[:-1]
diff --git a/fastNLP/core/samplers/reproducible_sampler.py b/fastNLP/core/samplers/reproducible_sampler.py
index c3facbb9..c8425dc7 100644
--- a/fastNLP/core/samplers/reproducible_sampler.py
+++ b/fastNLP/core/samplers/reproducible_sampler.py
@@ -20,6 +20,8 @@ class ReproducibleSampler:
      或者 batch_sampler；注意，所有在 init 中初始化的变量，都不能含有 _ 下横线作为开头；所有不在 init 中设置的变量都必须以下横线开头。
 
     """
+    def __init__(self, **kwargs):
+        self.num_replicas = 1
 
     def set_distributed(self, num_replicas, rank, pad=True):
         raise NotImplementedError("Each specific sampler should implement its own `set_distributed` method.")
@@ -47,14 +49,6 @@ class ReproducibleSampler:
     def set_epoch(self, epoch):
         pass
 
-    @property
-    def num_repliacs(self):
-        return self._num_replicas
-
-    @num_repliacs.setter
-    def num_repliacs(self, value):
-        self._num_replicas = value
-
 
 class RandomSampler(ReproducibleSampler):
     def __init__(self, dataset, shuffle: bool = True, seed: int = 0, **kwargs):