可以用CMD的SET命令来查看现有的系统变量，“="前的部分用%括起来就是。

常用：
%USERPROFILE% =C:\Users\用户名
%SystemRoot% =C:\WINDOWS
%SystemDrive% =C:
%APPDATA% =C:\Users\用户名\AppData\Roaming
%LOCALAPPDATA% =C:\Users\用户名\AppData\Local
%windir% =C:\WINDOWS
%Path% =C:\Windows\system32;C:\Windows;
%ProgramData% =C:\ProgramData
%ProgramFiles% =C:\Program Files
%ProgramFiles(x86)% =C:\Program Files (x86)

其他：
%ALLUSERSPROFILE% =C:\ProgramData
%CommonProgramFiles% =C:\Program Files\Common Files
%CommonProgramFiles(x86)% =C:\Program Files (x86)\Common Files
%CommonProgramW6432% =C:\Program Files\Common Files
%COMPUTERNAME% =MyPC
%ComSpec% =C:\WINDOWS\system32\cmd.exe
%HOMEDRIVE% =C:
%HOMEPATH% =\Users\用户名
%LOGONSERVER% =\MicrosoftAccount
%OS% =Windows_NT
%ProgramW6432% =C:\Program Files
%PUBLIC% =C:\Users\Public
%TEMP% =C:\Users\用户名\AppData\Local\Temp
%TMP% =C:\Users\用户名\AppData\Local\Temp
%USERDOMAIN% =MyPC
%USERNAME% =用户名