A composite bipolar plate for a polymer electrolyte membrane membrane fuel cell (PEMFC) is prepared as follows: a) melt compounding a polypropylene resin and graphite powder at 100-250° C. and 30-150 rpm to form a melt compounding material, the graphite powder content ranging from 50 wt % to 95 wt % based on the total weight of the graphite powder and the polypropylene resin, and the polypropylene resin being a homopolymer of propylene or a copolymer of propylene and ethylene, wherein 0.05-20 wt % carbon nanotubes, based on the weight of the polypropylene resin, are added during the melt compounding; and b) molding the melt compounding material from step a) to form a bipolar plate having a desired shaped at 100-250° C. and 500-4000 psi.