Web application modeling and implementation method are related with middleware platform tightly, and its models usually can?t be reused on different platform. In order to reuse web application models, it is necessary to raise the level of abstraction of models, constructing middleware platform independent models. Roles are meant to capture observable behavioral aspects of objects. Role models describe the set of valid object collaboration tasks. This paper proposes a method for constructing platform independent models for Web applications. It consists of a stepwise process, a template role model and a mapping from role model to class model. The method can improve the reusability of models at different level of abstraction. The paper shows how the method works by a simple example