I will go to Canton Fair.. is there any place i can buy souvenier such as keychain, shirt, and bag.

You can go to the Shangxiajiu Street, where you can buy these things. People there can speak mandarin and a little English. You can go shopping there without problem. While if there is local people for your accompany, you can bargain to get a better price.

Have you check the Beijing road(北京路)？ for souvenir and also you can call yourself actully had been to Guangzhou then :)