The process method of alkaline and acidic nickel plating combination is studied on AZ40M magnesium alloy. The high-corrosion resistance Ni-P coating is prepared to meet the corrosion and conductive technology requirements of spacecraft magnesium alloy electronic structure products. The properties of the Ni-P plating are studied by scanning electronic microscope(SEM) and its energy dispersive spectroscopy(EDS), X-ray diffraction (XRD), electrochemical polarization curves and neutral salt spray experiment. The result shows that the plating is amorphous structure and the phosphorus content is about 8%. The self-corrosion potential of magnesium alloys reached -0.55 V above and the corrosion current density declined obviously, and it is not eroded by neutral salt spray experiment for 48 h, when the electroless nickel time is more than 60 min, which indicates that the plating is dense and has excellent corrosion resistance to ensure the reliability of spacecraft electronic structure products on the ground storage, experiment and space application.