Ok, I think I have resolved the question. I put "LC_ALL=zh_CN.UTF-8" in my ~/.xinitrc so that gnome-session can not find correct config-file somewhere. Then it set XMODIFIERS=@im=ibus for me, which is not expected. After removing LC_ALL assignment, I can type Chinese in gnome-terminal again!
But, thank you too. And you can ignore this question.