A method for preparing a rare-earth permanent magnetic material with grain boundary diffusion using a composite target by vapor deposition, comprising: step 1 of: preparing the composite target having the chemical formula of H 100-x-y M x Q y, wherein: H is Dy or/and Tb, M is Nd or/and Pr, Q is one or more elements selected from the group of Cu, Al, Zn and Sn, x being in the range of 0 to 20 and y being in the range of 0 to 40 are atom percentage of corresponding composition in the composite target, and x and y can not be zero simultaneously; step 2 of: machining a sintered NdFeB magnet to the magnet with required shape and size, and then cleaning the surface of the magnet and drying, thereby obtaining a NdFeB magnet to be treated; step 3 of: alternately stacking the composite target and the NdFeB magnet to be treated in turn and being placed in a processing equipment, both of the topmost layer and the bottommost layer being the composite targets, coating the surface of the NdFeB magnet to be treated with the metal film under the specified condition using the composite target as an evaporation source and generating grain boundary diffusion, and then cooling along with the processing equipment, thereby obtaining a NdFeB magnet which has generated diffusion; and step 4 of: tempering the NdFeB magnet which has generated diffusion to uniformly coat the outside of the primary phase particles with the grain boundary phase, thereby obtaining a magnet of which the performance is improved; characterised in that the composite target is Tb 95 Cu 5, Tb 98 Al 2 or Tb 95.9 Dy 0.4 Nd 0.7 Zn 2 Sn 1. step 1 of: preparing the composite target having the chemical formula of H 100-x-y M x Q y, wherein: H is Dy or/and Tb, M is Nd or/and Pr, Q is one or more elements selected from the group of Cu, Al, Zn and Sn, x being in the range of 0 to 20 and y being in the range of 0 to 40 are atom percentage of corresponding composition in the composite target, and x and y can not be zero simultaneously; H is Dy or/and Tb, M is Nd or/and Pr, Q is one or more elements selected from the group of Cu, Al, Zn and Sn, x being in the range of 0 to 20 and y being in the range of 0 to 40 are atom percentage of corresponding composition in the composite target, and x and y can not be zero simultaneously; step 2 of: machining a sintered NdFeB magnet to the magnet with required shape and size, and then cleaning the surface of the magnet and drying, thereby obtaining a NdFeB magnet to be treated; step 3 of: alternately stacking the composite target and the NdFeB magnet to be treated in turn and being placed in a processing equipment, both of the topmost layer and the bottommost layer being the composite targets, coating the surface of the NdFeB magnet to be treated with the metal film under the specified condition using the composite target as an evaporation source and generating grain boundary diffusion, and then cooling along with the processing equipment, thereby obtaining a NdFeB magnet which has generated diffusion; and step 4 of: tempering the NdFeB magnet which has generated diffusion to uniformly coat the outside of the primary phase particles with the grain boundary phase, thereby obtaining a magnet of which the performance is improved; characterised in that the composite target is Tb 95 Cu 5, Tb 98 Al 2 or Tb 95.9 Dy 0.4 Nd 0.7 Zn 2 Sn 1.