i have 11-inch MacBook Air and my microsoft office doesn't work ,what should i do?

What version of the Mac OS are you using? (Look under the Apple menu and select About this Mac). What version of Mac Office are you using?

Office 2008 and Office 2011 are compatible with Mac OS 10.7 and 10.8 (Lion and Mt Lion). Previous versions are not.

My first thought was your version of office was incompatible but that's not the case. Try reinstalling office. You can download it from mactopia.com if you don't have the installer.