The densed-Ni coatings on sintered NdFeB magnets was prepared by high-energy ball milling method, and the densed-Ni coating was tested by film/substrate bonding force and Vickers hardness. The corrosion resistance of the magnets was studied by neutral salt spray test and high temperature PCT test. The corrosion process of the magnets was further analyzed by static full immersion test. The results showed that the Ni coating on the magnet surface could be densified by ball milling process. The microhardness of Ni-D24/NdFeB magnet increased from 427.95 HV to 502.67 HV and the binding force increased from 16.30 Mpa to 23.85 Mpa at 400 rpm and 24 h ball milling time, which indicated better mechanical damage resistance. The self-corrosion current density of the coating reduced by one order of magnitude compared with that of Ni/NdFeB magnet, and the resistance time to neutral salt spray increased from 312 h to 480 h, showing better corrosion resistance.