The magnetic properties and microstructure of sintered R–Fe–B (R, rare earth) magnets with nominal composition of ((PrNd)1−xMMx)30FebalB1 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.7; MM, misch metal) prepared using dual-alloy method were investigated. For x = 0.3, the maximum energy product ((BH)max) of the sintered magnet is higher than 318.4 kJ·m−3, but intrinsic coercivity (Hcj) is lower than 351.8 kA·m−1. The La and Ce contents are obviously different in some matrix-phase grains, which proves that the multi-hard magnetic phases (La, Ce-rich and La, Ce-lean) exist in the magnets. The coercivity is improved by the method of doping PrNd nanoparticles without sacrificing other magnetic properties. An enhancement in coercivity from 517.2 to 872.9 kA·m−1 is achieved by doping 5 wt% PrNd nanoparticles. Meanwhile, it could exhibit better magnetic properties (remanence Br = 1.332 T, intrinsic coercivity Hcj = 872.9 kA·m−1, maximum energy product (BH)max = 318.6 kJ·m−3) and make the distribution of the intergranular phase become more homogeneous.