Abstract: In grid computing system, the trust relation between resource vendor and resource user is the premise of safe communication, for the traits on distribution and dynamic, the trust between each other in advance is impossible, however, it can be resolved by importing trust mechanism to RBAC in Grid community, the trust degree of each Grid entity can be counted based on the feedback from other entities,and then their roles are changed based on their trust degrees.Using this policy, the dynamic trait can be realized in Grid and the cheat behavior of Grid entity also can be avoided.

Key words: Urid,Trust mecharusm,Role-based access control