The invention discloses a micron-scale elemental copper catalyst and a preparation method and application thereof. According to the key points of the technical scheme, the micron-scale elemental copper catalyst is prepared by the steps of reacting copper salt with an organic ligand to form a precursor and then performing calcination under the protection of nitrogen at the temperature of 400 to 800 DEG C, wherein the molar mass ratio of the copper salt (n) to the organic ligand (n) is (1-4) to 1, the copper salt is Cu(NO3)2.3H2O, and the organic ligand is 1,3,5-trimesic acid, terephthalic acid, isophthalic acid, phthalic acid, formic acid or 4,4',4''-s-triazine-1,3,5-three-para aminobenzoic acid. The invention further discloses the preparation method of the catalyst and the application of the catalyst to processing of nitrophenol waste water. The micron-scale elemental copper catalyst has the advantages of environmental friendliness, simple preparation process, high innovativeness and practicability and the like, nitrophenol pollutants in organic waste water can be effectively catalyzed and degraded, and the catalyst has circulating renewable use performance.