The eletrochemical properties of Cu eletrochemical polishing in phophoric acid solutions has been studied by anodic polarization and electrochemical impedance spectroscopy ( EIS) technique. The roughness of Cu firstly decreased, and then increased with the concentration of H₃PO₄increased at 0 . 2 V, 0 . 4 V, 0 . 6 V and 0 . 8 V, and reached the minimum roughness value when the H₃PO₄concentration was 55 % . The R_s value at different potential, fitting results of EIS, suggested the change in the resistance of viscous phosphate and Cu oxide films. With the increase of phosphate concentration, the relaxation time of the first capacitive semicircle extended, and it mean the acceleration in the copper dissolution reaction.