It’s very important to help developers design user interface for application in an intelligent user interface. Nowadays, the number of mobile based applications increases greatly, but there are no proper user model to guide the design and development of user interface. This article takes different types of functions and parameters in consideration, and proposes a user model and user modeling method based on activity theory. In addition, this article describes the improved VSM algorithm in detail. Finally, an application and an informal experiment are designed to prove the efficiency of given user model. This work can be used to guide the design and development of mobile user interface under mobile environment.