This paper introduced an XML-Based Unified User Interface System which implemented under Sun A4icrosystems's J2EE Architecture. Because more and more systems are transfer to web applications, and in the Post PC period, people want to get information at anywhere, anytime. So we would like to build a system, which can support multiple Internet devices. Because of the nature difference between each devices agent, it is a hard to develop a single system that can serve each device. Each Internet devices has its different technology to display information, such like HTML, WML, and etc. We try to build a unified user interface model, which can reduce duplicate works and put 00 design in our system. In this paper we will first dilate the main idea of this system and we will introduce XML technology and J2EE Architecture that used in this system, and then a brief introduction in WAP (Wireless Application Protocol) technology. Second we will introduce our related work Third, we will introduce our work in the system. Finally, express our conclusions, and future work.