The invention discloses fishbone-shaped core-shell structure nanometer nickel-copper alloy powder and a preparation method thereof, and belongs to the technical field of preparation of nanometer alloy materials. Sodium borohydride and/or potassium borohydride are/is used as reducing agents, nickel and copper ions in a metal salt solution are subjected to complexing so as to be turned into bluish violet sticky nickel-copper precursors through ethidene diamine at first, and then metal copper and nickel ions in the bluish violet sticky nickel-copper precursors are reduced into copper atoms and nickel atoms through the reducing agents at the temperature of 70-110 DEG C; the metal atoms gather and grow constantly, and finally nanometer nickel-copper alloy particles with special fishbone-shaped appearances and core-shell structures are obtained and can be used for manufacturing functional elements such as magnetic recording elements, sensors, ferrofluid elements and electromagnetic absorption elements. The preparation process of the nickel-copper alloy powder is simple, operation is simple and convenient, the reaction temperature is low, control over the shapes of the metal alloy particles can be achieved, and application prospects are broad.