Currently very few non-aqueous pseudocapacitor electrode materials are available. Organic matter based electrodes hold a great promise but remain largely unexplored. In this work, Ketjenblack carbon supported polyanthraquinone with different carbon to polymer ratios was prepared and evaluated as the pseudocapacitor electrode material in acetronitrile. These composite electrodes exhibit large specific capacitance up to 650F/g and specific capacity up to 270mAh/g when normalized to the polymer mass, which is much greater than other non-aqueous supercapacitor materials. They also have improved cycling stability with more than 85% capacitance retention after 1000 cycles as a result of the diminished quinone solubility in the electrolyte. When paired with a graphene-based positive electrode in asymmetric supercapacitors, composite electrodes demonstrate significant energy density up to 45.5Wh/kg and power density up to 21.4kW/kg. Their great supercapacitive performance, together with their low costs as well as structural and property diversities, makes them highly appealing for future energy storage applications.