As the power unit of automobile, fuel cell system should be stable and highly efficient under different load conditions in variable environment. Under different load conditions, operation parameters of fuel cell system have different impact on its performance. Correct operation parameters should be employed to make sure fuel cell system operates in high-efficiency zone. Orthogonal tests are employed to analyze the effect of operation parameters, such as flow rate, pressure, temperature, on the performance of the high-pressure fuel cell system. Some conclusions are derived from the tests. Air flow rate has less effect on the performance of fuel cell system, however, with the increase of current, the effect increases slightly. Air pressure has greater impact on the performance of fuel cell system, and such impact is remarkable when the current is low. Hydrogen pressure always has little effect. Operation temperature has very great impact on the performance of fuel cell system, and with the rise of temperature, its impact is more and more great. With the increase of current, the effect of temperature is also gradually increasing, and it becomes the only significant affecting factor when the current is high. © Journal of Mechanical Engineering.