The invention provides a preparation method of a porous nickel-alloy hydrogen evolution reaction composite cathode material, and the preparation method is mainly applied to the technical field of hydrogen evolution reactions. A powder reaction synthesis method is adopted, Ni, Fe, Mo, C and LaNi5 are prepared according to a certain ratio, the prepared powder is mixed evenly, 0.5-4% of stearic acid is added into the powder, a green body is obtained through pressure forming after drying is conducted and is subjected to vacuum sintering through the principle of solid-phase partial diffusion, and then the Ni-Fe-Mo-C / LaNi5 porous nickel-alloy hydrogen evolution reaction composite cathode material is obtained, wherein the content of the Fe, Mo, C and LaNi5 powder accounts for 22.5-52% of the total content. The porous nickel-alloy hydrogen evolution reaction composite cathode material prepared through the method has the advantages of being large in specific surface area, low in hydrogen evolution overpotential, good in catalytic property, good in corrosion resistance, stable in working performance, simple and environmentally friendly in preparation process, and the like, and has a significance to development of hydrogen energy sources.