Abstract: To improve the power performance and the fuel economy of a natural gas engine, the spark advance angle of the natural gas engine was optimized in this paper. A simulation model of the natural gas engine was developed based on GT-Power software. Through the theoretical analysis and the numerical simulation, the influences of the spark advance angle on in-cylinder pressure, in-cylinder temperature, rate of pressure rise, heat release rate, torque and brake specific fuel consumption were analyzed. Based on analysis, the spark advance angle of the supercharged natural gas engine was optimized by using DOE (design of experiments) and the map of the optimal spark advance angle was obtained under the conditions of full load and the air-fuel ratio of 22- 25, with the engine spark advance angle chosen as independent variables, the output torque chosen as the correlative variable, and appearance time of peak value of in-cylinder pressure and the rate of pressure rise chosen as constraint conditions.