The contributions of cloud computing in the prevention of software piracy are inadequate, and there are still rampant piratical mobile service applications in the cloud. This paper navigates mobile service application copyright protection in the cloud and sets a watermarking example to explain it. We use Monden's method to obfuscate the application's source code, remove a part of the semantics, and add it to a recovery module. Because these obfuscation rules come from watermarks, the watermarks are mapped into the rules. The recovery module is a recognizer to prove the watermarks when the original program is recovered. The experimental results indicate that the obfuscated code becomes difficult to reverse engineering and the watermarks are robust.