GUI-based analysis and testing methods of Android applications have become a research focus in recent years. Automation and high GUI coverage could improve the efficiency and effectiveness of most methods. However, previous work is insufficient to meet the requirements of automation and high GUI coverage. In this paper, we propose an automatic method of traverseing the GUIs in Android applications whose source codes are not available. The main idea of the method is to simulate user actions to explore the GUIs of an app automatically. The work tackles some key issues mainly in three aspects: extraction and process of UI elements, simulation of user actions, algorithm design and model building of GUI traversal. The result of experiments shows that the method is effective to traverse the GUIs of an application with a high GUI coverage. Furthermore, this method could assist other researches, such as program security analysis, GUI testing.