diff --git a/README.md b/README.md
index 3041b94..8367953 100644
--- a/README.md
+++ b/README.md
@@ -912,14 +912,35 @@ fbterm
 Install RealVNC
 
 ```
-dpkg --add-architecture armhf ; apt update
-cd ~/ ; wget https://www.realvnc.com/download/file/vnc.files/VNC-Server-6.6.0-Linux-ARM.deb
-apt install ./VNC-Server-6.6.0-Linux-ARM.deb
-rm -rf ./VNC-Server-6.6.0-Linux-ARM.deb
-dpkg --remove-architecture armhf ; apt update
-systemctl enable vncserver-x11-serviced.service ; systemctl start vncserver-x11-serviced.service
+sudo \
+sed -i '/deb http:\/\/mirrors.tuna.tsinghua.edu.cn\/debian\/ sid main non-free contrib/d' \
+/etc/apt/sources.list ; \
+apt clean all ; \
+echo 'deb http://mirrors.tuna.tsinghua.edu.cn/debian/ sid main non-free contrib' \
+>>/etc/apt/sources.list ; \
+dpkg --add-architecture armhf ; apt update \
+cd ~ ; wget https://www.realvnc.com/download/file/vnc.files/VNC-Server-6.6.0-Linux-ARM.deb \
+apt install ./VNC-Server-6.6.0-Linux-ARM.deb \
+rm -rf ./VNC-Server-6.6.0-Linux-ARM.deb \
+dpkg --remove-architecture armhf ; apt update \
+systemctl enable vncserver-x11-serviced.service ; \
+systemctl start vncserver-x11-serviced.service ; \
+sudo \
+sed -i '/deb http:\/\/mirrors.tuna.tsinghua.edu.cn\/debian\/ sid main non-free contrib/d' \
+/etc/apt/sources.list ; \
+apt clean all ; apt update
 ```
 
+**Attention please!!**
+
+```
+sudo \
+sed -i '/deb http:\/\/mirrors.tuna.tsinghua.edu.cn\/debian\/ sid main non-free contrib/d' \
+/etc/apt/sources.list ; \
+```
+
+**Don't miss this command in the process of installing RealVNC on it above!!!**
+
 Click [here](https://www.realvnc.com/en/connect/download/viewer/) to download RealVNC client
 
 Install and run the client, enter the IP address directly, do not need to fill in the port, username, and password is your system's login user and password.