Finding the user-interested concepts of a large ontology is an important problem in Ontology analysis and reusing. A set of ranked concepts of an Ontology, which are ordered by the potential degree-of-interest, can help person find out the expected concepts, especially when the target Ontology is complex and large. In this paper we present a concept ranking algorithm for OWL (Web Ontology Language) Ontologies. This algorithm is based on the ontological structure and degree-of-interest calculation. Different from the other ranking methods, it let user participate into the ranking process. Such an approach considers both the preference of a person and the graphical structure of the Ontology. The experimental results show that it can give comfortable ranking based on users' tasks and needs.