Abstract: Polyaniline electrodes doped with quaternary ammonium salts [CnH2n+1N(CH3)3]Cl(n=12,14,16,18) were prepared by cyclic voltammetry. The surface morphology and the structures of composite electrodes were characterized by scanning electron microscope(SEM) and Fourier transform infrared spectroscopy(FTIR). The electrochemical properties of electrodes and the capacitive behavior of the resulting capacitors were systematically studied using cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and constant current charge discharge tests. The specific capacitance of polyaniline electrode doped with [C18H37N(CH3)3]Cl exhibits a value as high as 329.6 F/g, higher than the value of 199.0 F/g for the PANI electrode at a constant current of 2×10-3 A. Moreover, the PANI/C18C3 electrodes retain good stability over 30 charge-discharge tests with a specific capacitance of 252.4 F/g.