A three dimensional model was proposed to study water transport phenomena in the membrane as well as the performance of PEMFC under various relative humidity(RH)of anode inlet gas.This model couples the conservation equations of the water concentration in membrane and the catalyst layer using a set of internal boundary conditions at the interface.The model was realized based on the COMSOL software and the simulated polarization curves are found in good agreement with the experiments thus confirming the validity of the model.The numerical results show that the humidification strongly influences the current density so as to affect the cell efficiency.Under low humidification conditions of anode inlet gas

the membrane current density below rib is greater than the gas flow channel

however

under the high humidity conditions

membrane current density distribution is uniform.Using thicker film

such as Nafion 117

the membrane of anode side has the potential of dehydration under high current density even if anode inlet gas be humidified.