App interface study on how to improve user experience

App interacts with users through graphical user interface. This paper focuses on the key factors of app interface design in thinking mode, interactive mode and visual mode of touch-screen smart phones and tablet PCs. The propose the idea is that user experience can be improved by the conversion of thinking mode, the innovation of interactive mode and more detailed design of visual mode. `E-Choice' was designed as an example to illustrate some of these ideas. It can be the reference for third-party companies in app development and interface design.