—Risk assessment is a very important tool to acquire a present and future security status of the network information system. Many risk assessment approaches consider the present system security status, while the future security status, which also has an impact on assessing the system risk, is not taken into consideration. In this paper we propose a novel risk assessment model based on Markov game theory. In this model, all of the possible risk in the future will impact on the present risk assessment. The farther away from now, the smaller impact on the risk assessment it has. After acquiring the system security status, we proposed an automatic generated reinforcement scheme which will provide a great convenience to the system administrator. A software tool is developed to demonstrate the performance of the risk assessment of a network information system and a simulation example shows the effectiveness of the proposed model. Keywords- risk assessment; Markov game theory; threat transm...