Hi my name is Mae, i am new in WOW and want to join the Shanghai server,
I see there are CN1 and CN2 and so on, which one is Shanghai? Is it CN1?
And after i decided can i change it in the future?

Thanks
Mae

Shanghai servers are CN1
Guangzhou are CN4
Beijing is CN2

That's all I know

Hmm, for now only few free transfers are available.
Check this out : https://www.battlenet.com.cn/account/management/fcm/eligible-realms.html?l=YOURACCOUNTNAME&r=CN

(I think you'll need to sign-in)

And after i decided can i change it in the future?

If you create a toon, say "ABC" on CN1 you most likely can't transfer "ABC" to another place, except as Hirna mentioned for the few free transfers.
What you can do, is create a new character, say "XYZ" on CN2, and so on. You are not bound to one server anymore like with the9.

hirna, just out of curiosity i tried that and no luck. i put my account name in the proper spot after it didn't work the lazy way too.

Actually you don't have to put your account name in the address but go to Battlenet.com.cn and sign in with your email address.
Then you should see some Burning Crusade pictures with ex-WoW account names under it. Click yours.

Then, there's this :

" Account Name 您的《魔兽世界》账号内尚有可用的游戏时间 "
and a little blue area right under this. On this blue area you'll find your game remaining time and 3 links. Clink on the third one (角色转移). You should arrive on a page where you can find 4 different links (the same font size and color as the link on the previous page--The last of the links being "FAQ").
Click 可选服务器 (3rd link).

And here you go, all the Realms supported by free transfer service.