Abstract:PEM fuel cells separate hydrogen into protons and electrons to generate electric power with electrons flowing through outer circuit. Channel structures affect flowing activities of hyd rogen and oxygen and species distribution, and ultimately influ ence output current density. Fuel cells are simulated respectiv ely with single straight channel, parallel channel, single serpe ntine channel and composite serpentine channel,and species diffusion process in channel and output voltage varition are analyzed.Simulation compares working area of hydrogen, oxygen and byproduct, water, and discovers input rates effect on curent density and species consuming ratio. Finally, optimized channel structure and operating parameters are obtained to improve fuel cell performance.