The power grid dispatching management system supported by the province-prefecture-county integrated model can effectively realize unified dispatching，management and monitoring of the power grid.However，one of the most outstanding challenges in the system construction is how to ensure transmission security of vast quantities of information and data between different dispatching institutions and plants.In view of the problem of “role flood” in data transmission，an improved role based access control（RBAC）model with the access description method of “user-role-page-permission” is proposed，and an open-hierarchical user permission scheme is presented.By taking into account the construction of database，the definition of hierarchical institutions and the design of extended permission，this paper focuses on key techniques for the implementation of the hierarchical user permission scheme.The effectiveness of the scheme is shown by its successful application to the small plant management system of Yunnan province-prefecture-county integrated power grid.