diff --git a/README.md b/README.md
index 76c47c9..154db5c 100644
--- a/README.md
+++ b/README.md
@@ -6,9 +6,11 @@ This script will let you setup your own VPN server in no more than a minute, eve
 ### Installation
 Run the script and follow the assistant:
 
+#### if server system is version of ubuntu 18.04LST then neet install libsodium to support AES-256-GCM
+`sudo apt install libsodium23 libsodium-dev`
 
 #### install git
-`sudo apt install git`
+`sudo apt install git `
 
 
 #### clone code file and excute
@@ -23,9 +25,8 @@ This is foked from https://github.com/Nyr/openvpn-install.
 
 Changed cipher type and lan ip range.
 
-Tps:
+#### Tips:
 
-```
 The system of server and client must be supported AES-256-GCM. I try successed in Ubuntu 19.04 from google cloud.
-And the version of ubuntu 18.04TLS is not supported.
-```
+And the version of ubuntu 18.04TLS is not supported, need install libsodium.
+I didn't try other system.