The invention relates to a catalyst of supported metal phosphide, in particular to a process for preparing the catalyst of high dispersive supported metal phosphide. The catalyst is composed of two parts of active components and a carrier which can be represented by AP/Z or B2P/Z, wherein the A of the active components is Mo or W, the B of the active components is Ni or Co, and the Z of the carrier is Al2O3 or SiO2. The operation steps of the catalyst are that transient metal salt and mammonium dihydrogen phosphate are dissolved in deionized water according to the stoichiometric ratio of targeted phosphide, and simultaneously moderate hydroxy acid as chelating agent is added to get the impregnating solution for preparing supported transition metal phosphide. The porous carrier is immersed in the impregnating solution, and is rested, the procedure gains temperature and returns after the impregnating solution is dried, roasted and under the atmosphere of hydrogen gas, and finally the supported transition metal phosphide is made. The supported transition metal phosphide prepared by the preparation method has the advantages of high dispersion, simple and convenient operation, low cost, no pollution, good repeatability and easiness of large scale preparation.