diff --git a/fastNLP/core/dataset.py b/fastNLP/core/dataset.py
index 668bb93e..5e72106f 100644
--- a/fastNLP/core/dataset.py
+++ b/fastNLP/core/dataset.py
@@ -54,12 +54,6 @@ class DataSet(object):
             else:
                 raise AttributeError('{} does not exist.'.format(item))
 
-        def __setattr__(self, key, value):
-            if hasattr(self, 'fields'):
-                self.__setitem__(key, value)
-            else:
-                super().__setattr__(self, key, value)
-
         def __repr__(self):
             return "\n".join(['{}: {}'.format(name, repr(self.dataset[name][self.idx])) for name
                               in self.dataset.get_fields().keys()])
@@ -205,17 +199,23 @@ class DataSet(object):
         return [name for name, field in self.field_arrays.items() if field.is_target]
 
     def __getattr__(self, item):
-        if item in self.field_arrays:
-            return self.field_arrays[item]
-        elif item in _READERS:
+        # block infinite recursion for copy, pickle
+        if item == '__setstate__':
+            raise AttributeError(item)
+        try:
+            return self.field_arrays.__getitem__(item)
+        except KeyError:
+            pass
+        try:
+            reader_cls = _READERS[item]
             # add read_*data() support
             def _read(*args, **kwargs):
-                data = _READERS[item]().load(*args, **kwargs)
+                data = reader_cls().load(*args, **kwargs)
                 self.extend(data)
                 return self
 
             return _read
-        else:
+        except KeyError:
             raise AttributeError('{} does not exist.'.format(item))
 
     @classmethod
@@ -269,3 +269,6 @@ if __name__ == '__main__':
     _ = d.a
     d.apply(lambda x: x['a'])
     print(d[1])
+    import copy
+    dd = copy.deepcopy(d)
+    print(dd.a)