Abstract: Based on TBAC and RBAC, this article synthesized advantages of both and proposed one kind of new model, namely T_RBAC-Based CSCW System Access Control Model.The model continues to use RBAC as the system overall structure and adds the concept of task in original RBAC.After connecting role and task, permission and task, it realizes the dynamic management authority by the method of the task.Introduced the exterior state of the work flow to the access control model to work with the internal state of the task, the model controls the assignment of task permission′s it meet the joint work characteristic of the CSCW system.