The invention relates to the technical field of industrial catalysis, and provides a preparation method of a vanadium phosphorus oxide catalyst. The method comprises the following steps: preparing a metal assistant-doped oxovanadium hydrogenphosphate hemihydrate catalyst precursor powder, wherein the metal assistant is at least one of Fe, Mo, Co, Ce, Zr, Nb, and Ni, and a molar ratio of the metal assistant to vanadium is 0.06 to 0.15; and mixing the catalyst precursor powder with a binder and an auxiliary material, and carrying out strip extrusion or tabletting molding to obtain the vanadium phosphorus oxide catalyst, wherein the binder is at least one of phosphoric acid, pyrophosphoric acid, trimethyl phosphate, triethyl phosphate, aluminum dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, zinc phosphate, tricalcium phosphate, ammonium phosphate, ammonium pyrophosphate and ammonium hexametaphosphate, the auxiliary material is at least one of graphite, carbon nanotubes, graphene and carbon powder, and a mass ratio of the catalyst precursor powder to the binder to the auxiliary material is 100:(0.1-15):(0.1-10). The preparation method of vanadium phosphorus oxide catalyst is simple and has no special requirements of production devices, and the obtained catalyst has the advantages of high strength, good catalytic effect, and facilitation of industrial production and application.