In the distributed computing environments, users would like to share resources and communicate with each other to perform their jobs more efficiently. For better performance, it is important to keep resources and the information integrity from the unexpected use by unauthorized users. Therefore, there is a strong demand for the access control of distributed shared resources in the last few years. Role-Based-Access-Control (RBAC) has been introduced and has offered a powerful means of specifying access control decisions. In this paper, we propose an object-oriented RBAC model for distributed system (ORBAC), it efficiently represents the real world. Moreover, under the decentralized ORBAC management architecture, an implementation of the model has realized multiple-domain access control. Finally, statically and dynamically role authorization has been considered and a method to deal with the problem of seperation of duties has been presented.