The invention relates to a preparation method of a high-performance sintered Nd-Fe-B permanent magnet material, belonging to the field of rare earth permanent magnet material. The quaternary and abovequaternary rare earth alloy films are deposited on the surface of pretreated Nd-Fe-B magnet by magnetron sputtering. The homogenization, grain boundary diffusion and low temperature tempering are used as diffusion sources to improve the boundary structure of the magnet, so that the coercivity of the magnet is greatly increased and the remanence is kept basically unchanged. The composition of thequaternary and above quaternary rare earth alloy film is LRE 100-X-Y-ZHRExMyAlz (1 <= x <= 40, 1 <= y <= 20, 1 <= z <= 20), wherein LRE is one or more of the light rare earth elements such as Y, La, Ce, Pr, Nd, HRE is one or more of the heavy rare earth elements such as Tb, Dy, Ho, and M is one or more of the alloy elements such as Cu, Fe, Co, Ga, Zr, Zn, Mn, and Mg. The rare earth alloy thin filmprepared by the invention is uniform, compact and strong in adhesion as diffusion source, the quantity is continuously controllable, and the consistency of magnetic properties of the magnet after diffusion treatment is good; It can reduce the amount of rare earth and is suitable for industrial production.