Abstract: The magnetic properties of sintered neodymium iron boron magnets made of Dy70Cu15Ga15 alloy with grain boundary diffusion were studied using magnetron sputtering technology, as well as the microstructure changes and corrosion behavior characterization in the electrochemical environment. Research has shown that grain boundary diffusion treatment can significantly improve the coercivity of magnets. The coercivity of magnets has significantly increased from 15.86 kOe to 19.46 kOe, with an improvement rate of 22.7%, while residual magnetism and maximum magnetic energy product remain basically unchanged. The diffusion of Dy element mainly enters the grain boundary phase of the magnet, optimizes the distribution of grain boundary phase, and exists in the defect zone of the main phase grain boundary, replacing the Nd element in the main phase, forming (Nd, Dy) 2Fe14B phase, enhancing the anisotropic field of the defect layer, and suppressing the nucleation of demagnetized domains. The substitution of Nd elements into the grain boundary region increases the proportion of non-magnetic phases, effectively isolating adjacent main phases and weakening magnetic coupling. The eutectic diffusion of low melting point CuGa alloy opens up diffusion channels, improves the diffusion efficiency of Dy, and optimizes the grain boundary structure. After diffusion, the main phase diffraction peak of the sample shifts towards a larger angle, resulting in better grain orientation; The Dy70Cu15Ga15 alloy magnet forms a more stable and higher corrosion potential rich Dy rare earth phase at the grain boundaries, optimizing the intergranular structure of the magnet and improving its corrosion resistance.