As a method that can significantly improve the coercivity of sintered NdFeB magnets and realize the high-quality utilization of heavy rare earth, grain boundary diffusion has increasingly become a research hotspot in the field of rare earth permanent magnetism and industry. In this paper, the influence of substrate composition difference on the magnetic properties of the magnets after grain boundary diffusion during the batch preparation of the grain boundary diffusion sintered magnets has been studied by using the automatic spraying equipment system. The results of microstructure and EDS element analysis show that the difference in the growth range of the coercivity of the magnets after grain boundary diffusion is closely related to the adequacy of the formation of the grain core-shell structure in the magnets after diffusion, the uniform distribution of the grain boundary phase and the content of ferromagnetic elements in the grain boundary phase, At the same time, the temperature coefficient of the magnet prepared by the grain boundary diffusion process is better than that of the magnet of similar brand prepared by the traditional process. Keywords: Sintered NdFeB magnets; Grain boundary diffusion process; Magnetic properties