Neodymium iron boron magnet and preparation method thereof

The present invention, on the one hand, provides a neodymium iron boron magnet, comprising neodymium iron boron magnet blank and the RTMH alloy layer compounded on the surface; the R is one or more selected from rare earth elements; the T is Fe and/or Co; the M is one or more selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pt, Au, Pb and Bi; the H is hydrogen element. By the present invention, the coercive force of magnets is significantly enhanced, and at the same time, the original magnetic remanence and maximum magnetic energy product of the magnets are not significantly reduced.