diff --git a/DrissionPage/__init__.py b/DrissionPage/__init__.py
index 5861945..1c99f50 100644
--- a/DrissionPage/__init__.py
+++ b/DrissionPage/__init__.py
@@ -13,4 +13,4 @@ from ._configs.chromium_options import ChromiumOptions
 from ._configs.session_options import SessionOptions
 
 __all__ = ['ChromiumPage', 'ChromiumOptions', 'SessionOptions', 'SessionPage', 'WebPage', '__version__']
-__version__ = '4.0.0b19'
+__version__ = '4.0.0b20'
diff --git a/DrissionPage/_pages/chromium_tab.py b/DrissionPage/_pages/chromium_tab.py
index 907c60b..983ee4a 100644
--- a/DrissionPage/_pages/chromium_tab.py
+++ b/DrissionPage/_pages/chromium_tab.py
@@ -304,7 +304,7 @@ class WebPageTab(SessionPage, ChromiumTab, BasePage):
                         self.get(url)
 
     def cookies_to_session(self, copy_user_agent=True):
-        """把driver对象的cookies复制到session对象
+        """把浏览器的cookies复制到session对象
         :param copy_user_agent: 是否复制ua信息
         :return: None
         """
@@ -313,7 +313,7 @@ class WebPageTab(SessionPage, ChromiumTab, BasePage):
 
         if copy_user_agent:
             user_agent = self.run_cdp('Runtime.evaluate', expression='navigator.userAgent;')['result']['value']
-            self.session.headers.update({"User-Agent": user_agent})
+            self._headers.update({"User-Agent": user_agent})
 
         set_session_cookies(self.session, super(SessionPage, self).get_cookies())
 
diff --git a/DrissionPage/_pages/session_page.py b/DrissionPage/_pages/session_page.py
index 60d49f5..038bf38 100644
--- a/DrissionPage/_pages/session_page.py
+++ b/DrissionPage/_pages/session_page.py
@@ -49,6 +49,8 @@ class SessionPage(BasePage):
 
         elif isinstance(session_or_options, Session):
             self._session_options = SessionOptions()
+            self._headers = session_or_options.headers
+            session_or_options.headers = None
             self._session = session_or_options
 
     def _s_set_runtime_settings(self):
@@ -305,12 +307,12 @@ class SessionPage(BasePage):
         parsed_url = urlparse(url)
         hostname = parsed_url.hostname
         scheme = parsed_url.scheme
-        if not check_headers(kwargs, self.session.headers, 'Referer'):
+        if not check_headers(kwargs, self._headers, 'Referer'):
             kwargs['headers']['Referer'] = self.url if self.url else f'{scheme}://{hostname}'
         if 'Host' not in kwargs['headers']:
             kwargs['headers']['Host'] = hostname
 
-        if not check_headers(kwargs, self.session.headers, 'timeout'):
+        if not check_headers(kwargs, self._headers, 'timeout'):
             kwargs['timeout'] = self.timeout
 
         kwargs['headers'] = {**self._headers, **kwargs['headers']}
diff --git a/DrissionPage/_pages/web_page.py b/DrissionPage/_pages/web_page.py
index 748ccf7..3b08d1a 100644
--- a/DrissionPage/_pages/web_page.py
+++ b/DrissionPage/_pages/web_page.py
@@ -274,7 +274,7 @@ class WebPage(SessionPage, ChromiumPage, BasePage):
 
         if copy_user_agent:
             user_agent = self.run_cdp('Runtime.evaluate', expression='navigator.userAgent;')['result']['value']
-            self.session.headers.update({"User-Agent": user_agent})
+            self._headers.update({"User-Agent": user_agent})
 
         set_session_cookies(self.session, super(SessionPage, self).get_cookies())
 
diff --git a/DrissionPage/_units/setter.py b/DrissionPage/_units/setter.py
index 705bc1d..cfca821 100644
--- a/DrissionPage/_units/setter.py
+++ b/DrissionPage/_units/setter.py
@@ -253,12 +253,12 @@ class SessionPageSetter(BasePageSetter):
 
     def encoding(self, encoding, set_all=True):
         """设置编码
-        :param encoding: 编码名称
-        :param set_all: 是否设置对象参数，为False则只设置当前response
+        :param encoding: 编码名称，如果要取消之前的设置，传入None
+        :param set_all: 是否设置对象参数，为False则只设置当前Response
         :return: None
         """
         if set_all:
-            self._page._encoding = encoding
+            self._page._encoding = encoding if encoding else None
         if self._page.response:
             self._page.response.encoding = encoding
 
diff --git a/DrissionPage/_units/setter.pyi b/DrissionPage/_units/setter.pyi
index a82eaeb..45faf59 100644
--- a/DrissionPage/_units/setter.pyi
+++ b/DrissionPage/_units/setter.pyi
@@ -5,7 +5,7 @@
 """
 from http.cookiejar import Cookie
 from pathlib import Path
-from typing import Union, Tuple, Literal, Any
+from typing import Union, Tuple, Literal, Any, Optional
 
 from requests.adapters import HTTPAdapter
 from requests.auth import HTTPBasicAuth
@@ -100,7 +100,7 @@ class SessionPageSetter(BasePageSetter):
 
     def timeout(self, second: float) -> None: ...
 
-    def encoding(self, encoding: str, set_all: bool = True) -> None: ...
+    def encoding(self, encoding: Optional[str, None], set_all: bool = True) -> None: ...
 
     def cookie(self, cookie: Union[Cookie, str, dict]) -> None: ...
 
diff --git a/setup.py b/setup.py
index 1ca634c..ed2a7d6 100644
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@ with open("README.md", "r", encoding='utf-8') as fh:
 
 setup(
     name="DrissionPage",
-    version="4.0.0b19",
+    version="4.0.0b20",
     author="g1879",
     author_email="g1879@qq.com",
     description="Python based web automation tool. It can control the browser and send and receive data packets.",