Abstract: The microalloying effect of niobium on the microstructure and magnetic properties of an Nd₂Fe₁₄B nanocrystal permanent magnet was investigated. The results show that niobium addition promotes the formation of amorphous phase and stabilizes the amorphous phase. During the annealing, precipitate phase after niobium adding restrains the growth of grains, uniforms the size of grains, and enhances the magnetic properties of the alloy. The optimum magnetic properties of J_r=0. 899 8 T, H_ci=912.64 kA· m^-1 and (BH)_m=126.24 kJ·m^-3 were obtained by annealing a melt-spun Nd_12.3Fe_80.7NbB_6.0 amorphous ribbon at 550℃ for 10 min. But the magnetic properties decreased when the annealing temperature further increased.