Grid computing emerges as an effective technology to couple geographically distributed resources and solve large-scale computational problems in wide area networks.Each famous international grid project is constructed with a specific grid platform,and different grid projects manage different distributed resources/services.In order to aggregate resources managed by different grid platforms,it's necessary to implement the interoperation among these grid platforms.Security is one of key issues for the interoperation.Current popular grid platforms have such common properties as global user identity and virtual organization.In this paper,interoperation mapping policy and security interoperation process are proposed based on grid common properties.CGSP(ChinaGrid Support Platform)and GOS(Grid Operating System)are two popular grid platforms in China.Taking security interoperation between CGSP and GOS as an example,the implementation of interoperation mapping policy and security interoperation process are introduced.Authorization consistency,flexibility of mapping policies and the security of the interoperation process are analyzed.Finally,grid interoperation process between grid platforms also is analyzed.