In the distributed environment, users would like to communicate with each other and share resources. Role-based access control is one of the effective means to protect resources in a security system. Based on analyzing the object-oriented RBAC model, and introducing PMI attribute certificate, an object-oriented RBAC model based on it (AC-ORBAC) is proposed for multiple domains by using attribute certificate. The access control is more flexible, and also the separation of duty is discussed. Moreover, an implementation with PKI is given.