The present invention discloses a rare earth permanent magnet material and a preparation method thereof The method comprises: a sintering treatment step: laying a composite powder for diffusion on the surface of a neodymium iron boron magnetic powder layer and carrying out spark plasma sintering treatment to obtain a neodymium iron boron magnet with a diffusion layer solidified on the surface thereof, wherein the compositional proportional formula of the composite powder for diffusion is H100-x-yMxQy, where H is one or more of a metal powder, a fluoride powder, or an oxide powder of Dy, Tb, Ho, and Gd, M is a Nd, Pr, or NdPr metal powder, and Q is one or more of Cu, Al, Zn, and Sn metal powders, x and y are respectively the atomic percentages of component M and component Q in the composite powder for diffusion, x is 0-20, and y is 0-40; and diffusion heat treatment and tempering steps. The method of the present invention has high efficiency, good diffusion effects, and reduced quantities of heavy rare earth elements.