The Information Grid (IG) presented in this article is aimed at providing different units in the multiple virtual organizations (VO) with uniform information safely and rapidly, accurately and reliably. Its security frame takes up the designing idea and implementation of GSI, especially in communication protection, authentication and agency certification mechanisms. Yet the GSI authorization is not suitable for information grid stream as it is too simple and its supplement of the authorization mechanism CAS is too centralized. According to the Role-based Access Control (RBAC), the VO authorization service strategy (VOAS) is presented, by which the problems of the delicate authorization and extensibility of globus are solved. The result of simulations shows that the VOAS strategy will not affect the efficiency of the system, and instead, the complexity of the accessing control is reduced.