A method of preparing a high-coercivity sintered NdFeB magnet including cerium comprising the following steps: Providing alloy flakes composed of R x T (1-x-y-z) B y M z wherein R is at least one of Nd, Pr, Ho, and Gd; T is at least one of Fe and Co; and M is at least one of Mg, Ti, Zr, Nb, and Mo; and x, y, and z are 28.0wt% ≤ x ≤ 33.0wt%, 0.8wt% ≤ y ≤ 1.2wt%, and Owt% ≤ z ≤ 3.0wt%; Mixing the alloy flakes, a low melting point powder, and a lubricant, then subjecting the mixture to a hydrogen embrittlement process followed in this order by pulverizing the process product to an alloy powder by jet milling, magnetic field orientation molding of the alloy powder to obtain a blank, sintering and aging treatment the blank, and cutting the obtained sintered NdFeB magnet into the desired shape, wherein the low melting point powder is at least one of Ce α Al 100-α with 90≤α≤99, Ce β Cu 1-β with 80≤β≤99, and Ce γ Ga 1-γ with 80≤γ≤99 and wherein a content of the Ce in the mixture is in the range of 1 to 10 wt% based on a total weight of the alloy flakes and the low melting point powder; Coating a film composed of a diffusion source of formula R1 x R2 y H z M 1-x-y-z on the sintered NdFeB magnet, wherein R1 is at least one element of Nd and Pr; R2 is at least one element of Ho and Gd; H is at least one element of Tb and Dy; M is at least two elements of Al, Cu, Ga, Ti, Co, Mg, Zn, and Sn; and x, y, and z are 5.0wt% < x < 50.0wt%, Owt% < y ≤ 15.0wt%, and 30.0wt% ≤ z ≤ 90.0wt%; and Performing a diffusion heat treatment so as to diffuse the diffusion source into the sintered NdFeB magnet, followed by aging the sintered NdFeB magnet to obtain the low-cost rare earth magnet. Providing alloy flakes composed of R x T (1-x-y-z) B y M z wherein R is at least one of Nd, Pr, Ho, and Gd; T is at least one of Fe and Co; and M is at least one of Mg, Ti, Zr, Nb, and Mo; and x, y, and z are 28.0wt% ≤ x ≤ 33.0wt%, 0.8wt% ≤ y ≤ 1.2wt%, and Owt% ≤ z ≤ 3.0wt%; Mixing the alloy flakes, a low melting point powder, and a lubricant, then subjecting the mixture to a hydrogen embrittlement process followed in this order by pulverizing the process product to an alloy powder by jet milling, magnetic field orientation molding of the alloy powder to obtain a blank, sintering and aging treatment the blank, and cutting the obtained sintered NdFeB magnet into the desired shape, wherein the low melting point powder is at least one of Ce α Al 100-α with 90≤α≤99, Ce β Cu 1-β with 80≤β≤99, and Ce γ Ga 1-γ with 80≤γ≤99 and wherein a content of the Ce in the mixture is in the range of 1 to 10 wt% based on a total weight of the alloy flakes and the low melting point powder; Coating a film composed of a diffusion source of formula R1 x R2 y H z M 1-x-y-z on the sintered NdFeB magnet, wherein R1 is at least one element of Nd and Pr; R2 is at least one element of Ho and Gd; H is at least one element of Tb and Dy; M is at least two elements of Al, Cu, Ga, Ti, Co, Mg, Zn, and Sn; and x, y, and z are 5.0wt% < x < 50.0wt%, Owt% < y ≤ 15.0wt%, and 30.0wt% ≤ z ≤ 90.0wt%; and Performing a diffusion heat treatment so as to diffuse the diffusion source into the sintered NdFeB magnet, followed by aging the sintered NdFeB magnet to obtain the low-cost rare earth magnet.