The operating parameters of the PEM fuel cell stack have an impact on the performance of the stack output as well as the parasitic power of auxiliary devices such as air compressor， recirculation pump and cooling fan. System maximum net power output goals can be achieved by optimizing the operating parameters of the fuel cell stack. Forthe actual system， constrained by the performance of the air compressor and the regulating capacity of the backpressure valve， the adjustment range of cathode operating parameters is limited. In this paper， the 62 kW fuel cell system model is established based on MATLAB/Simulink. Through simulation analysis， the achievable ranges of parameters optimization under various load currents are determined. Genetic algorithm is employed to optimize the fuel cell stack temperature， cathode pressure， and oxygen excess ratio. The results show that increasing the temperature of the fuel cell stack at various load currents is advantageous for enhancing the system's net power， with the optimal operating temperature being 80 ℃. However， the optimization direction for the oxygen excess ratio and cathode pressure varies at different load currents. At low load current （50， 100 A）， increasing the oxygen excess ratio and cathode pressure results in a smaller growth in stack output power compared to the parasitic power. Providing lower oxygen excess ratio and cathode pressure is advantageous for enhancing the net power of the system. At high load current （300 A）， low oxygen excess ratio and cathode pressure will limit the output power of the stack， with the lowest net power of only 35.530 kW. After the oxygen excess ratio and cathode pressure are reasonably increased， the optimal net power is 53.271 kW， and the net power can be increased by 49.9% through the optimization of operating parameters.