The invention discloses a method for preparing nanometer copper oxide. The method includes dissolving cuprous chloride raw materials in ammonia water, adding beta-ethoxy acetic ester into the ammoniawater to obtain mixtures, then placing the mixtures in a closed reaction kettle, carrying out stirring reaction, then filtering reaction products, and washing obtained filter residues by hot purifiedwater to obtain cuprous chloride particles; preparing copper nitrate solution, adding the cuprous chloride particles into the copper nitrate solution, carrying out slurrying, adding urea into the copper nitrate solution, stirring and dissolving the urea to obtain mixtures, placing the mixtures into a high-pressure reaction kettle, carrying out high-temperature and high-pressure stirring reaction,filtering reaction products to obtain third filter liquid and third filter residues and washing the third filter residues by hot purified water to obtain copper oxide filter residues; carrying out vacuum drying on the copper oxide filter residues which are washed by the aid of the hot water, crushing the copper oxide filter residues by the aid of airflow and screening the copper oxide filter residues by the aid of screen cloth with the sizes of 150-250 meshes so as to obtain the nanometer copper oxide. The method has the advantages that the method includes simple processes and is low in cost and high in production efficiency, and the nanometer copper oxide prepared by the aid of the method is good in dispersibility, uniform in particle size distribution, high in purity and low in impuritycontent.