Language Support

Yes the actual program does. You just goto edit>Preferences>General tab and beside "Language" set it to traditional chinese. This changed the program, like menus, and all to chinese BUT NOT SONG NAMES OR THE ITUNES STORE PAGE.

Does anyone know if the iTune supports Traditional
Chinese or not?

If you are talking about song names, this requires that you have Asian language support enabled on your OS and also the ID3 tags encoded correctly (Unicode).

http://homepage.mac.com/thgewecke/mlingos9.html#itunes