The invention belongs to the technical field of electrocatalytic hydrogen evolution material preparation, and relates to a preparation method for constructing a two-dimensional metal-organic frameworks (MOFs) nano-hydrolysis electrocatalyst based on foamy copper. The preparation method comprises the following steps: based on foamy copper, carrying out the in-situ growth of flower-like copper phosphate nanosheets on the surface of foamy copper through a self-sacrificing template method at first; and then, carrying out the in-situ growth of copper-bearing MOFs nanosheets on the surface of foamycopper based on the copper phosphate nanosheets grown on the surface of foamy copper, wherein the copper-bearing MOFs nanosheets are perpendicular to Cu3(PO4)2 nanosheets. The preparation method provided by the invention has the beneficial effects that foamy copper is adopted as a reaction base, has a three-dimensional network macro-porous structure, and is stable in structure, rich in material source and low in price; through the structural design of the base and the adoption of the self-sacrificing template method for the in-situ growth of the MOFs nanosheets, no extra metal sources need tobe added, the preparation process is simple and controllable, and the structure of the catalyst grown on the surface of the base is stable; and the morphology of a composite material is changed by regulating and controlling the reaction time and the reaction temperature, the ultra-thin MOFs nanosheets are formed, and the specific surface area and the active site exposure ratio are high.