Once upon a time, I see on some document telling that "updating the host field of user record to % can enable user connect to the mysql database from any host", so I followed the guide,tried from other side and failed.
Today I finally found the reason:
You need exec reload to make the change take effect using "./mysqladmim -uroot -p<your password> reload"
So I can connect from other PC to the mysql Server.
Just trick, but very useful.