im looking for some open source xbox project, I just wanna join it and try myself as game programmer, does anybody know such project?
First off, this is a question and answer site, rather than a project finding site.
Secondly, you can only get an SDK for the Xbox if you are a licensed developer and pay a lot. So I doubt you'll find an open source one.
However, you can create Xbox Live Community Arcade (?) games with XNA and C#, for $99 a year for a license. They won't be open source, but you can join them. Gamedev's help wanted forum is good.