Currently a large number of web services as well as other kinds of services such as EJBs, COM, and even Java Classes are made available to the general public. Facilitating the SOA based system development by leveraging such kinds of services becomes a challenge. A framework for service repository, ontology based service discovery and service composition is put forward. The service repository can maintain the web services, EJBs, and Java Classes with the functions such as service registration, publishing, discovery, matching, versioning, and monitoring. The details of service description are analyzed. A domain ontology for Procurement, Selling, and Inventory is also given. Based on the domain ontology and the service repository, the semantic enhanced service composition algorithm is discussed.