Abstract: As an important component of high-level secure operating systems, the privilegecontrol mechanism can provide an appropriate level of security assurance for the system. It presents a multi-layered privilege control mechanism implemented in Ansheng OS V4.0, a copyrighted security operating system that satisfies all the specified requirements of criteria class 4, “Structured-Protection”, in GB17859-1999 (equally, the B2 level in TCSEC). This mechanism enforces privilege control and management in the user-level, function-level and program-level of the system, and it can make the system implementation responsibility separation with roles defined in the role-based access control policy, dynamic functionality separation with domains defined in the domain and type enforcement policy, least privilege principle required by the POSIX standard and therefore ensure the security of the system with the use of privilege in such a controlled manner.