[en] Polyaniline/multi-walled carbon nanotubes composites were synthesized by an in situ chemical oxidative polymerization method and were the new electrode materials used for supercapacitor. The composites were characterized physically by transmission electron microscope and X-ray diffraction. The electrochemical capacitance performance of the composites in neutral solution (NaNO₃) was investigated by cyclic voltammetry, galvanostatic charge-discharge tests and ac impedance spectroscopy with a three-electrode system. The polyaniline/multi-walled carbon nanotubes composites electrodes showed much higher specific capacitance (328 F g^-1), better power characteristics and were more promising for application in capacitor than pure polyaniline electrodes. This may be attributed to the introduction of multi-walled carbon nanotubes. The improvement mechanisms of multi-walled carbon nanotubes in the composites electrode were also discussed in detail