The invention discloses core-shell structure copper-coated iron nanometer composite powder and a preparation method and application thereof. The nanometer composite powder is of a core-shell structure, the core of the core-shell structure is nanometer iron powder, and the shell is a nanometer copper film. According to the preparation method, cupric acetate is dissolved in dimethylformamide, and a cupric acetate solution is obtained; the nanometer iron powder is added into the cupric acetate solution during stirring and heated to 40-70 DEG C; after constant-temperature reaction, solid and liquid are separated, and the core-shell structure copper-coated iron nanometer composite powder is obtained. According to the application, the composite powder is formed in a pressed mode through a common powder metallurgy technology, the density of the materials is larger than or equal to 7.1 g / cm<3> after sintering, and the grain size is smaller than or equal to 5 microns. The method is simple, operation is convenient, quality is stable, and the process is controllable. The prepared nanometer composite powder is completely wrapped. The preparation system is low in oxygen content, the preparation process is safe and stable, and the prepared copper-coated iron nanometer composite powder is stable in property, high in oxidation resistance and capable of being produced in batches, thereby being proper raw materials for preparing high-performance nanometer powder metallurgy materials.