Most Web applications are developed under tight schedules and in a rapidly evolving environment. The maintenance of such applications becomes problematic as the complexity of the Web application grows. Creating appropriate design and architecture models is the key for efficiently managing and supporting the evolution of Web applications. Researchers have identified the need to apply reverse engineering techniques to already existing Web applications to create abstract design models. The reverse engineering of Web sites has been addressed in various ways. In this paper, we propose OntoWer, an ontology-based Web application reverse engineering approach to deduce the conceptual schema of Web application. Starting from an analysis Web HTML pages, it uses domain ontology to generate a conceptual schema for modeling the corresponding Web application. It consists of three phases: i) the extraction of candidate elements, ii) the identification of relevant ontological constructs, and iii) the generation of conceptual schema of the Web application