diff --git a/fastNLP/io/data_bundle.py b/fastNLP/io/data_bundle.py
index 1f05cf68..ba275e61 100644
--- a/fastNLP/io/data_bundle.py
+++ b/fastNLP/io/data_bundle.py
@@ -10,6 +10,7 @@ from typing import Union
 
 from ..core.dataset import DataSet
 from ..core.vocabulary import Vocabulary
+from ..core._logger import logger
 
 
 class DataBundle:
@@ -47,13 +48,14 @@ class DataBundle:
         self.vocabs[field_name] = vocab
         return self
 
-    def set_dataset(self, dataset, name):
+    def set_dataset(self, dataset, name: str):
         """
 
         :param ~fastNLP.DataSet dataset: 传递给DataBundle的DataSet
         :param str name: dataset的名称
         :return: self
         """
+        assert isinstance(dataset, DataSet), "Only fastNLP.DataSet supports."
         self.datasets[name] = dataset
         return self
 
@@ -64,7 +66,13 @@ class DataBundle:
         :param str name: dataset的名称，一般为'train', 'dev', 'test'
         :return: DataSet
         """
-        return self.datasets[name]
+        if name in self.datasets.keys():
+            return self.datasets[name]
+        else:
+            error_msg = f'DataBundle do NOT have DataSet named {name}. ' \
+                        f'It should be one of {self.datasets.keys()}.'
+            logger.error(error_msg)
+            raise KeyError(error_msg)
 
     def delete_dataset(self, name: str):
         """
@@ -83,7 +91,13 @@ class DataBundle:
         :param str field_name: 名称
         :return: Vocabulary
         """
-        return self.vocabs[field_name]
+        if field_name in self.vocabs.keys():
+            return self.vocabs[field_name]
+        else:
+            error_msg = f'DataBundle do NOT have Vocabulary named {field_name}. ' \
+                        f'It should be one of {self.vocabs.keys()}.'
+            logger.error(error_msg)
+            raise KeyError(error_msg)
 
     def delete_vocab(self, field_name: str):
         """
@@ -94,6 +108,14 @@ class DataBundle:
         self.vocabs.pop(field_name, None)
         return self
 
+    @property
+    def num_dataset(self):
+        return len(self.datasets)
+
+    @property
+    def num_vocab(self):
+        return len(self.vocabs)
+
     def set_input(self, *field_names, flag=True, use_1st_ins_infer_dim_type=True, ignore_miss_dataset=True):
         """
         将field_names中的field设置为input, 对data_bundle中所有的dataset执行该操作::
@@ -238,7 +260,7 @@ class DataBundle:
                 self.vocabs.pop(field_name)
         return self
 
-    def iter_datasets(self)->Union[str, DataSet]:
+    def iter_datasets(self) -> Union[str, DataSet]:
         """
         迭代data_bundle中的DataSet
 
@@ -252,7 +274,7 @@ class DataBundle:
         for name, dataset in self.datasets.items():
             yield name, dataset
 
-    def iter_vocabs(self)->Union[str, Vocabulary]:
+    def iter_vocabs(self) -> Union[str, Vocabulary]:
         """
         迭代data_bundle中的DataSet
 
@@ -266,7 +288,7 @@ class DataBundle:
         for field_name, vocab in self.vocabs.items():
             yield field_name, vocab
 
-    def apply_field(self, func, field_name:str, new_field_name:str, ignore_miss_dataset=True,  **kwargs):
+    def apply_field(self, func, field_name: str, new_field_name: str, ignore_miss_dataset=True,  **kwargs):
         """
         对DataBundle中所有的dataset使用apply_field方法
 
@@ -313,11 +335,11 @@ class DataBundle:
     def __repr__(self):
         _str = ''
         if len(self.datasets):
-            _str += 'In total {} datasets:\n'.format(len(self.datasets))
+            _str += 'In total {} datasets:\n'.format(self.num_dataset)
             for name, dataset in self.datasets.items():
                 _str += '\t{} has {} instances.\n'.format(name, len(dataset))
         if len(self.vocabs):
-            _str += 'In total {} vocabs:\n'.format(len(self.vocabs))
+            _str += 'In total {} vocabs:\n'.format(self.num_vocab)
             for name, vocab in self.vocabs.items():
                 _str += '\t{} has {} entries.\n'.format(name, len(vocab))
         return _str