Abstract: In this paper,the degradation mechanisms of PEMFC idling conditions are analyzed,and the influence of the different degradation mechanisms of idling conditions on the parameters of the fuel cell model are identified. Using the established twodimensional isothermal multi-physical model for the PEMFC,the performance of the fuel cell before and after the degradation under idling conditions and the contribution of various degradation factors to the voltage attenuation and the change of internal reaction gas distribution are simulated. The results show that the increase in cathode activation loss is the most important degradation factor under idling conditions,followed by open-circuit voltage（OCV）degradation,and the least impact is the cathode ECSA degradation. Under the same operating conditions,the minimum oxygen molar concentration and the minimum hydrogen molar concentration of the fuel cell increase and the current density maldistribution increases after the degradation.