diff --git a/docs/faq.rst b/docs/faq.rst
index a42bae1d..dde1a211 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -8,6 +8,15 @@ FAQ
 设置环境变量 ``PYPINYIN_NO_PHRASES=true`` 即可
 
 
+如何禁用默认的“拼音库”copy 操作
+++++++++++++++++++++++++++++++++
+
+设置环境变量 ``PYPINYIN_NO_DICT_COPY=true`` 即可.
+
+
+副作用: 用户的自定义拼音库出现问题时, 无法回退到自带的拼音库.
+
+
 ``INITIALS`` 声母风格下，以 ``y``, ``w``, ``yu`` 开头的汉字返回空字符串
 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
diff --git a/pypinyin/constants.py b/pypinyin/constants.py
index 95309b5f..c4d3872a 100644
--- a/pypinyin/constants.py
+++ b/pypinyin/constants.py
@@ -16,10 +16,16 @@
     PHRASES_DICT = {}
 else:
     from pypinyin import phrases_dict
-    PHRASES_DICT = phrases_dict.phrases_dict.copy()
+    PHRASES_DICT = phrases_dict.phrases_dict
 
 # 单字拼音库
-PINYIN_DICT = pinyin_dict.pinyin_dict.copy()
+PINYIN_DICT = pinyin_dict.pinyin_dict
+
+# 利用环境变量控制不做copy操作(无自定义拼音库的情况), 以减少内存使用
+if not os.environ.get('PYPINYIN_NO_DICT_COPY'):
+    PINYIN_DICT = PINYIN_DICT.copy()
+    PHRASES_DICT = PHRASES_DICT.copy()
+
 # 匹配使用数字标识声调的字符的正则表达式
 RE_TONE2 = re.compile(r'([aeoiuvnm])([1-4])$')
 
diff --git a/tests/_test_env.py b/tests/_test_env.py
index 53dc3c58..69a470bf 100644
--- a/tests/_test_env.py
+++ b/tests/_test_env.py
@@ -2,7 +2,9 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
+from importlib import reload
 import os
+
 os.environ['PYPINYIN_NO_PHRASES'] = 'true'
 
 import pypinyin.core  # noqa
@@ -11,3 +13,15 @@
 def test_env():
     assert pypinyin.core.PHRASES_DICT == {}
     assert pypinyin.core.seg('北京') == ['北京']
+
+
+def test_no_copy():
+    """ 禁用 copy 操作 """
+    reload(pypinyin.constants)
+    assert pypinyin.core.PINYIN_DICT is not pypinyin.pinyin_dict.pinyin_dict
+
+    os.environ['PYPINYIN_NO_DICT_COPY'] = 'true'
+    reload(pypinyin.constants)
+    assert pypinyin.constants.PINYIN_DICT is pypinyin.pinyin_dict.pinyin_dict
+
+