Particle refinement is the effective way to improve the coercive force without increasing the HRE content in Sintered Nd-Fe-B magnets. The magnetic properties and initial magnetization permeability has been investigated in order to correlate the particle refinement by traditional powder metallurgy method with nominal composition of (Pr₂₅Nd₇₅)₂₅Dy₆Al_0.5B₁Co₁Cu_0.2Fe_bal sintered Nd-Fe-B magnet. The particles with average size of 3.0 μm achieved the best Hcj, and the particles with average size of 3.5 μm obtained the best Br respectively. Refined particle size which made the morphology regular and uniform. But with further decreased the average particle size, Nd rich phase was in the form of oxide, and unevened distribution in the grain boundary, and the demagnetization coupling efficiency droped, results in the decrease of Hcj. The oxidation content increased with the average size becoming samller, the Br decreased with the impurity content increased. On the other hand,the initial permeability dramatically fallen with the impurity content.