H+ and Fe3+ ions co–doped polyaniline were synthesized by cyclic voltammetry onto the stainless steel mesh with various concentration of ferric chloride (FeCl3·6H2O) in electrolyte. The structure and morphology of PANI and PANI/Fe3+ films were characterized by Fourier transform infrared (FT–IR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical properties of PANI and PANI/Fe3+ films were investigated by cyclic voltammetry, galvanostatic charge–discharge test and electrochemical impedance spectroscopy (EIS) in 0.5molL−1 H2SO4 electrolyte in three–electrode system. The PANI/0.2M Fe3+ film shows a larger specific capacitance of 602F g−1 at a current density of 3mA/cm2 and lower resistance compared with the pure PANI film. The relationship between electrochemical properties of a serious of transition metal ions doped PANI/Mn+ (Mn+ =Mn2+, Co2+, Ni2+, Cu2+, Zn2+ and Fe3+) films and the ratio of electronic affinity and ionic radius (Ea/r) has also been researched.