This master thesis project studies behavior and actions of older users in China, with emphasis on the influence of vision decrease on older peopleʼs using experience. Related data was collected through the action research process and user behavior was studied. The project can be divided into two parts: user study and action research. In the user study section, user problems were posed and studied thoroughly with three user investigation methods: questionnaire, interview and ethnographic observation. Analysis was then carried out according to the study outcomes. Based on the user study results, action research direction was elicited to mainly focus on three aspects: font and icon study, as well as touch-screen interaction pattern research. Contextual inquiry was adopted as the primary research method; “Text-in-screen” prototype; “Look and feel” prototype and the platform iOS were used as tools to complete the research. At the end, explicit criteria of fonts and icons that better suits older users with poor vision was established and usersʼ adaptability for touch-screen smart phone system was explored.