Service oriented architecture is an approach to build distributed systems that deliver application functionality as services to end-user applications or to build other value-added services. The adoption of service oriented architecture will help enterprises achieve an agile e-business environment to provide customers flexible services by integrating required application functionalities dynamically and seamlessly. However, the dynamic and loosely coupling nature will raise many trust concerns of the service computing technology e.g. QoS and security issues. In this paper, we propose a framework for trust computing by extending trusted platforms with service oriented architecture. We employ Trusted Computing Group's trusted computing platform as the foundation of the framework and apply cryptography infrastructure as the enabling technologies to secure all interactions among service requesters, service providers and service registries. Based on the enabling technologies, we can further divide service level trust concerns into three layers namely service description and publishing, service discovery and composition and service execution and monitoring. We also provide guidelines for each separate trust concern in the three layers correspondingly.