The α-Fe/R2Fe14B-type nanocomposite magnets have been prepared by hot pressing melt spun Pr8Dy1Fe74.5Co10Nb0.5B6 flakes under a conventional pressure P of 125 MPa and high pressures ranging from 1 to 7 GPa. It was found that increasing compaction pressure from 125 MPa to 5 GPa led to marked grain refinement in the magnet and consequently resulted in significant improvement of magnetic properties. When hot pressing under even higher pressure (P≫5 GPa), however, the crystallization was constrained and the hot pressed magnets retained a certain amount of amorphous phase besides the Pr2Fe14B-type phase and α-(FeCo) phase, which resulted in the deterioration of the magnetic properties. A remanence of 11.1 kG, coercivity of 10.2 kOe, and maximum energy product of 23.6 MGOe have been achieved in the magnet hot pressed under a pressure of 5 GPa. © 2000 American Institute of Physics.