Abstract: In order to analyze the parameter sensitivity of proton exchange membrane fuel cell（PEMFC）,a three-dimensional,twophase,isothermal fuel cell model is established and investigated by COMSOL. The influence of ionomer volume fraction and back pressure on mass transfer and the battery performance are obtained by analyzing material concentration distribution,polarization curve and power density curve. The results show:with the increase of ionomer volume fraction,the performance of battery is improved duc to the weakening of Ohmic polarization loss;with the decrease of the operating voltage,the amplitude of the current density increases;the performance of battery is improved with increasing of back pressure;the effect of cathode back pressure on performance is greater than that of the anode back pressure.