Service-oriented computing is becoming a direction of computing technology. For realising the mission of serviceoriented computing, service-oriented architecture has been proposed to facilitate the application development via discoverable services distributed on Internet. That brings out service-oriented modelling as a new technical area to provide modelling and analysis techniques of service-oriented applications. The paper proposes a framework for agentbased service-oriented modelling. It treats both the service providers and the service requesters as service agents. Domain ontology has been used to provide the sharable domain knowledge as well as terminology for allowing the agents to understand each others. A modelling process has also been illustrated with the model development of an online auction service.