RBACAM, a role-based administrative model of RBAC, is proposed in this paper. It simplifies the description of role hierarchies with the definition of role identity code and role derivative information pair group. The concept of role administration domain and role enhanced administration domain is introduced to realize decentralized administration of RBAC. Each role has responsibility for role administration in its own administration domain and enhanced administration domain. A series of conflict checking rules to maintain consistency and the administration of authorization constraints are provided in the model. Administrative algorithms of role hierarchies, userrole assignments, permission-role assignments and authorization constraints are also described. RBACAM can be applied in the context of the RBAC96 model without introducing additional entities and relations. The main advantage of RBACAM is its simplicity, completeness and practicability.