A two-dimensional model of PEMFC with conventional flow field was established and the partial differential equations were solved based on the control-volume method. The effects of humidifying level on membrane conductivity and mass transfer were investigated.The numerical results indicated that total water drag coefficient increased when humidification in anode increased

and membrane conductivity was largely improved when humidification in anode was enhanced.Total water drag coefficient reduced when humidifying level in cathode increased.Humidification in anode was more important than that in cathode where the humidification effect was limited only to relatively low current density.The anode gas should be humidified as much as possible

when PEMFC operated at low current density.It is advisable to decrease the humidifying level of anode gas when operating at high current density to avoid two-phase flow in cathode so as to improve mass transfer.