Abstract: Electrode material is a major effect factor on performance of electrochemical capacitor,and high performance electrode material has become the focal point of research and development at present.Specific capacitance of carbon electrode material is low.Although the oxides of precious metals such as ruthenium give very high specific capacitance,they have the inherent disadvantage of high price.Therefore,cheap and environment-friendly transition-metal oxides known as excellent electrode materials for supercapacitors with high oxidation reduction capacitance have attracted many interests of researchers. Precursor was prepared via hydrothermal process with cobalt nitrate as raw material and citric acid as template.After thermal treatment at 200 ℃,cobaltosic oxide (Co<SUB>3</SUB>O<SUB>4</SUB>) was obtained.Electrochemical properties of prepared Co<SUB>3</SUB>O<SUB>4</SUB> electrode material were tested by cyclic voltammogram and galvanostatic charge/discharge measurements.Results showed Co<SUB>3</SUB>O<SUB>4</SUB> obtained at 200 ℃ has a good cycle stability in 6 mol/L KOH electrolyte with potential range from -0.1 to 0.5 V (vs.SCE).Its specific capacitance as single electrode was up to 442 F/g.This method provides a reference for development of high performance supercapacitor electrode material.