By using metallographic microscope, scanning electron microscope, X ray diffraction and other test methods, this paper studies the microstructure of brush silver coating prepared by multicomponent coordination systems, such as succinimide, 5,5-dimethyl hydantoin and mono potassium phosphate. The results show that the appearance of silver coating of cyanide free brush is silver white with uniform and even surface and the combination situation between silver coating and copper is great. The coating is the single silver particle structure whose arrangement is tight and size is small and even. It meets the requirements of microstructure of button contact used by high voltage switch and lays the theoretical basis for the development of electric brush plating repair technology of silver coating of button contact used by high voltage switch.