Electrochemical supercapacitors based on polyaniline (PANi) and polypyrrole (PPy) electrode materials are currently attracting significant interest on account of the high specific capacitance and electrical conductivity. In this work, three kinds of supercapacitor electrodes were fabricated by use of three nanocomposites synthesised by coating graphene sheets with PANi, PPy and their copolymer thin layers through in situ chemical oxidative polymerization, respectively, in which graphene sheets were used as the conductive substances for aniline and pyrrole. What’s more, in order to clearly understand their electrochemical performances, detailed electrochemical analysis was employed and the differences were compared. It is found that the nanocomposite prepared has wider electrochemical window, the higher specific capacitance values, excellent energy storage properties, low charge transfer resistance and high cycle–life stability, which exhibits high-performance characteristic for supercapacitor application.