Abstract: The effects of Heat Isostatic Pressing (HIP) sintering on the density, microstructure and magnetic properties of Nd-Fe-B permanent magnets were studied. The results show that compared to conventional magnets, the magnetic properties of HIP sintered ones decrease due to the deterioration of alignment of Nd₂Fe₁₄B grains and the lower density of the magnets, which resulted from the existence of more holes in the HIP sintered magnets. It is concluded that HIP sintering is not suitable for producing high performance sintered Nd-Fe-B magnets.