Abstract: The supercapacitor using nanosized α-MnO₂ and activated carbon as electrode materials was developed,and the synthesization of nanosized α-MnO₂ and the effect of the concentration of electrolyte on the performance were studied in detail. Three kinds of supercapacitors, MnO₂/KOH/MnO₂, AC/KOH/AC and MnO₂/KOH/AC, were prepared. Cyclic voltammetry (CV), galvanostatic charge-discharge and time constant technology were used to study the performance of the electrodes and the supercapacitors. The results showed that excellent performance of the electrods was found when the concentration of KOH solution was 7 mol•L^-1.Specific capacitance of α-MnO₂ could reach a value of 237 F•g^-1.The super-capacitors with AC electrode as negative electrode and asymmetric configuration had better characteristics than the ones composed of two identical AC or MnO2 electrodes. The operating voltage of α-MnO₂/KOH/AC hybrid super-capacitor was 1.5 V and had low self-discharge rate.