Software testing plays an important role in improving the security and reliability of mobile applications. However, there are many shortcomings in the current mainstream testing technology for mobile application. For example, manual scripting and recording playback techniques require a lot of labor costs, while automatic testing solutions have been limited when they are applied in mobile applications. This article presents a sketch-guided GUI test generation approach for testing mobile applications. It provides a simple but expressive sketch language to help testers specify their testing purposes easily. Testers just need to draw a few simple strokes on the corresponding screenshots of the application under test, then the proposed approach recognizes these strokes automatically and converts them into the test model. Finally, test cases are generated based on the model. The effects of proposed sketch-guided testing technique are evaluated based on the test cases, which were used in the literature of mobile application testing in recent years. The results show that the proposed approach is significantly effective with little labor cost in GUI testing of mobile applications.