A composite bipolar plate for a polymer electrolyte membrane fuel cell (PEMFC) is prepared as follows: a) compounding vinyl ester and graphite powder to form bulk molding compound (BMC) material, the graphite powder content ranging from 60 wt % to 95 wt % based on the total weight of the graphite powder and vinyl ester, wherein carbon nanotubes together with a polyether amine dispersant or modified carbon nanotubes 0.05-10 wt %, based on the weight of the vinyl ester resin, are added during the compounding; b) molding the BMC material from step a) to form a bipolar plates having a desired shaped at 80-200° C. and 500-4000 psi.