Clectrochemial reaction occurred on Ni(OH)2/NiOOH electrode was studied with electrochemical method and ellipsometry with wavelength sweep.Cobalt was implanted intosurface of nickel with fonim plantation technology to improve charge efficiency of the electrode. With fitting ellipemetric experimental data,transformation model of the surface film was obtainedduring charge and discharge. Implantation of cobalt did not affect the model,but made charge effi-ciency be increased.