Abstract: In view of the characteristic of the grid environment, a TSRBAC authorization model which is suitable the grid environment is proposed after analyzed the limitation of existing grid authorization mechanism and the access control models.The model improved the RBAC policy and realized the distributional management of permission and the dynamic authorization.It has satisfied the request that dynamic of the resources and independent of policy, and adapted the characteristic of the grid environment.This paper has given the concept definition and formal description of the model, and improved the CAS architecture with this model.