Security policy of multilevel security DBMS is expressed by many models.One of them is access control model.Mandatory Access Control (MAC) model guarantees that information flow in multilevel databases is inaccordance with security policy.Role-Based Access Control can simplify administration of privileges in multilevel databases.This paper proposes an integrated model of RBAC and MAC.Multilevel role and internal role are defined,and some modified operations in the model are presented.Administration of privileges under MAC policy is done by system automatically.The integrated model can simplify administration of privileges,and is appropriate for multilevel relation database system which has many users or complex security levels.Some implementing mechanisms of the model are provided.