An app in Android can collaborate with other apps and control personal information by using the Intent or user's allowing of permission. However, users cannot detect when they communicate. Therefore, users might not be aware information leakage if app is malware. This paper proposes DroidTrack, a method for tracking the diffusion of personal information and preventing its leakage on an Android device. DroidTrack alerts the user of the possibility of information leakage when an app uses APIs to communicate with outside. These alerts are triggered only if the app has already called APIs to collect personal information. Users are given the option to refuse the execution of the API if it is not appropriate. Further, by illustrating how their personal data is diffused, users can have the necessary information to help them decide whether the API use is appropriate.