Surface modification of graphite/phenolic resin (PF) composite plates with expanded graphite (EG) was studied in this paper.Both volume resistance and contact resistance of the modified composite bipolar plates decreasd obviously after modification.The effects of expanded volume and thickness of EG on volume resistance and contact resistance were investigated.The results showed that the expanded volume of EG was an important factor that influenced the volume resistance and contact resistance of modified composite plates.Contact resistance decreased at first and then tended to become unchanged with the increase of the thickness of EG.The reduction of contact resistance and volume resistance became even more remarkable with the increase of PF content in the modified composite plates.