Abstract: A series of petroleum coke-based superactivated carbons (SACs) was prepared by KOH activation. Electrochemical performance of the SACs and a porous carbon called YP15 (Kuraray Chemical Co., Japan) as electrodes of supercapacitors in aqueous and nonaqueous electrolytes were characterized and compared by chronopotentiograms, cyclic voltammetry and AC impedance spectrum analysis. It was found that the specific capacitances of SACs increased with surface area and the highest values in the electrolytes of KOH, H2SO4,(C2H5)4NBF4/propylene carbonate(PC), and (C2H5)4NBF4/acetonitrile, were 257F/g, 228F/g, 140F/g and 142F/g respectively, all greater than that of YP15. The ESR volume resistivities of the SACs were lower than that of YP15 in 1mol/L H2SO4, higher than that of YP15 in 1mol/L (C2H5)4NBF4/PC, and close to that of YP15 in 3mol/L KOH. The ESR volume resistivity of the SACs in 1mol/L (C2H5)4NBF4/acetonitrile, which was prepared at 800℃ for 3h using a KOH to petroleum coke ratio of 4∶1, was lower than that of YP15.