Abstract: CRUAC is based on usage control model, the concept of role is introduced into the model, and the constraint information is added to the decision-making factors in the model. The model can solve the complexity problems such as system development, reuse, system security management caused by assigning permissions to users directly in usage control model, and provides a solution to solve the problem of cloud users access resources which were stored in different cloud servers. The model can better meet the needs of Cloud computing environment in access control.