Application development for mobile computing devices has been greatly developed. The design of user interface is a complex and time-consuming job. In a pervasive computing environment, the program might be shown in different kinds of mobile computing devices. So an efficient method of interface development has become necessary. In this paper, we analyze shortcomings of traditional user interface design methods and propose a new software reuse technology to enhance the reusability and extensibility of mobile computing devices user interface which is based on XML. We use DTD to provide definitions of XML document type and define a XML document only to implement a unified user interface. The pages could be generated dynamically by using XSLT to analyze the XML documents and be shown in mobile client browsers. This reuse technology could select suitable XSLT styles for transforming an XML user interface description into different shapes to reduce the complexity of interface development and improve the efficiency of development.