Is it possible to use the JQuery effects in the existing Xcode project? plz let me knw if it is possible..
Short answer without more details is probably no, inasmuch as Objective-c is a compiled language that produces a runtime package that will run on the appropriate devices and JQuery is a set of javascript libraries that are interpreted when run in a browser or or on a server side javascript engine such as NodeJs.
It's possible you might be writing an application in Xcode that users a browser window so once you are inside a browser then the answer might be yes you can run JQuery inside that but this supposes that you are writing html/js inside this area.
THe other question would be why do you want to? If you are writing XCode then you have full access to all the Apple UI's which are native to the touch devices you are developing for and probably (certainly) give you a much wider set of options.