Objective: Developing New Rural Cooperative Medical System ( NCMS ) critical illness insurance is a relatively new operation mode for the government, which needs to provide quantify references for policy designers to help the predict decision. Methods: Through the analysis of decision process and behavior of the government and the commercial companies , the utility maximization functions for both the government and the commercial companies are set up based on the game theory. The Stackelberg model theory is then applied to figure out the relationship among different parameters in the utility maximization functions. Results and Conclusion: In the process of critical illness insurance under NCMS, the government should combine the local situation, to design reasonable polices based on the relationship among different parameters , so as to lead the NCMS critical illness insurance develop in a healthy way.