Because the current information-processing system security analysis of the dynamic monitoring is not mature enough, this paper will make use of finite state automata techniques to improve dynamic information flow monitoring methods, and design its monitors. This method is the use of finite state automata theory, information flow from the dynamic monitoring of proceeding through a secure stack to real-timely monitor the user's operation. This method can prevent high-density users through covert channel from leaking secrets to the low-density users and reach the purpose of Protection System confidentiality.