The present disclosure provides a method for increasing the coercivity of a sintered type NdFeB permanent magnet. The method comprises:

a) coating of a slurry on a surface of the magnet, the slurry comprising
first particles consisting of a heavy rare earth alloy or a heavy rare earth or a non-metallic compound, and
second particles consisting of a metal alloy or a meta,
wherein at least one of the first particles and second particles includes at least one of Dy and Tb and wherein a ratio of the average particle diameter between the second particles and the first particles is 2:1 to 20:1;
b) performing a vibration of the coated magnet in vertical direction of the applied slurry with a vibration frequency of 10 Hz to 50 Hz for 30 s to 5 min, then drying the slurry; and
c) performing a thermally induced grain boundary diffusion process.