Possible Duplicate:
Is there a way to convert an iOS app to a Mac OS X app?
I want to publish my iPad & iPhone apps on Mac desktop too, is it possible to do, if yes so for that what changes I need to do in my code.
iOS development is similar to Mac development but not the same: they use different GUI libraries (AppKit vs UIKit).
You could look into an open source solution such as Chameleon, which is UIKit reimplemented for Mac. It has some limitations but is also surprisingly impressive!
Otherwise, as others have said, you'll be rewriting your GUI.