The invention discloses a foamed nickel-loaded iron-cobalt-nickel metal nano-catalyst and a preparation method and application thereof. The method comprises the following steps: cutting foamed nickel,washing and drying for later use; dissolving three metal salts of cobalt nitrate, ferrous nitrate and nickel nitrate, ammonium fluoride and urea into deionized water; performing stirring to obtain ahydrothermal solution; then adding the pretreated foamed nickel and the prepared hydrothermal solution into a high-pressure reaction kettle, vertically putting the foamed nickel into the bottom of thehigh-pressure reaction kettle after the foamed nickel is inserted into a polytetrafluoroethylene base, fastening the high-pressure reaction kettle, putting the high-pressure reaction kettle into a blast drying oven, carrying out first-step hydrothermal treatment, performing cooling to room temperature, performing washing and drying to obtain an intermediate product; and putting the prepared precursor into a reaction kettle, carrying out a second-step hydrothermal reaction, performing cooling to room temperature, and performing washing and drying. The preparation method provided by the invention has good economy and environmental protection property, and the prepared product has excellent electro-catalytic oxygen evolution performance, high strength and good stability, and can be applied to the field of water electrolysis oxygen evolution.