A preparation method for an RTB-based permanent magnet material, wherein the preparation method comprises the following steps: the molten liquid of the raw material composition of the RTB-based permanent magnet material is subjected to casting, hydrogen decrepitation, and pulverization to obtain a powder, and the powder is mixed with dispersant, and then pressed, formed, sintered and aged; wherein: the raw material composition of RTB-based permanent magnet material comprises the following components by mass percentage: R': 29.5-33.5 wt.%, R' is a rare earth element, R' comprises Pr, the content of Pr is >_8.85 wt.%; X: 0-5.0 wt.%, X is one or more of Cu, Al, Ga, Co, Zr, Ti, Nb and Mn; B: 0.90-1.2 wt.%; Fe: 61.4-69.5 wt.%; in the process of pulverization, O ≤ 60 ppm in the pulverization atmosphere; in the pressing process, O ≤ 40 ppm in the pressing atmosphere; the dispersant comprises element C, and the mass percentage of the dispersant in the mixed powder is 0.04-0.2%; the molten liquid of the raw material composition of the RTB-based permanent magnet material is prepared by the following method: melting in a vacuum induction melting furnace; the vacuum degree of the melting furnace is 5×10 -2 Pa; the melting temperature is below 1500°C; the casting process is carried out as follows: cooling at a rate of 10 2 °C /s -10 4 °C/s in an Ar atmosphere; the pulverization is jet mill pulverization; the pressure in the pulverization chamber of the jet mill pulverization is 0.38 MPa; the time of the jet mill pulverization is 3 hours; the sintering is also preceded by preheating; wherein, the temperature of the preheating is 300-600°C, the time of the preheating is 1-2h; preferably, the preheating is preheating at 300°C and 600°C for 1h respectively; the temperature of the sintering is 1040-1090°C; the time of the sintering is 2h; the grain boundary diffusion treatment is also carried out after sintering and before the aging treatment; wherein, preferably, the grain boundary diffusion treatment is carried out according to the following steps, attaching substance containing Tb and/or containing Dy to the surface of the RTB-based permanent magnet material by evaporating, coating or sputtering, then carrying out diffusion heat treatment; the temperature of the diffusion heat treatment is preferably 800-900°C; the time of the diffusion heat treatment is preferably 12-48h; the treatment temperature of the aging treatment is 500-650°C; in the aging treatment, the heating rate of heating to 500-650°C is 3-5 °C/min; the treatment time of the aging treatment is 3h. the raw material composition of RTB-based permanent magnet material comprises the following components by mass percentage: R': 29.5-33.5 wt.%, R' is a rare earth element, R' comprises Pr, the content of Pr is >_8.85 wt.%; X: 0-5.0 wt.%, X is one or more of Cu, Al, Ga, Co, Zr, Ti, Nb and Mn; B: 0.90-1.2 wt.%; Fe: 61.4-69.5 wt.%; R': 29.5-33.5 wt.%, R' is a rare earth element, R' comprises Pr, the content of Pr is >_8.85 wt.%; X: 0-5.0 wt.%, X is one or more of Cu, Al, Ga, Co, Zr, Ti, Nb and Mn; B: 0.90-1.2 wt.%; Fe: 61.4-69.5 wt.%; in the process of pulverization, O ≤ 60 ppm in the pulverization atmosphere; in the pressing process, O ≤ 40 ppm in the pressing atmosphere; the dispersant comprises element C, and the mass percentage of the dispersant in the mixed powder is 0.04-0.2%; the molten liquid of the raw material composition of the RTB-based permanent magnet material is prepared by the following method: melting in a vacuum induction melting furnace; the vacuum degree of the melting furnace is 5×10 -2 Pa; the melting temperature is below 1500°C; the casting process is carried out as follows: cooling at a rate of 10 2 °C /s -10 4 °C/s in an Ar atmosphere; the pulverization is jet mill pulverization; the pressure in the pulverization chamber of the jet mill pulverization is 0.38 MPa; the time of the jet mill pulverization is 3 hours; the sintering is also preceded by preheating; wherein, the temperature of the preheating is 300-600°C, the time of the preheating is 1-2h; preferably, the preheating is preheating at 300°C and 600°C for 1h respectively; the temperature of the sintering is 1040-1090°C; the time of the sintering is 2h; the grain boundary diffusion treatment is also carried out after sintering and before the aging treatment; wherein, preferably, the grain boundary diffusion treatment is carried out according to the following steps, attaching substance containing Tb and/or containing Dy to the surface of the RTB-based permanent magnet material by evaporating, coating or sputtering, then carrying out diffusion heat treatment; the temperature of the diffusion heat treatment is preferably 800-900°C; the time of the diffusion heat treatment is preferably 12-48h; the treatment temperature of the aging treatment is 500-650°C; in the aging treatment, the heating rate of heating to 500-650°C is 3-5 °C/min; the treatment time of the aging treatment is 3h.