The invention provides a nickel powder preparation method. The nickel powder preparation method comprises the steps that a nickel salt solution and an ammonium oxalate solution are added into a base solution to be subjected to reaction, and nickel oxalate is obtained; the nickel oxalate is subjected to reduction, and a nickel powder crude product is obtained; the nickel powder crude product is added into a nickel acetate solution and/or a nickel formate solution and is made to adsorb nickel acetate and/or nickel formate, and the nickel powder crude product obtained after adsorption is filtered and dried; and the nickel powder crude product obtained after adsorption is subjected to reduction, and nickel powder is obtained. The invention provides application of the nickel powder prepared through the nickel powder preparation method in 3D printing and powder metallurgy. According to the nickel powder preparation method and application of the nickel powder, the process combining liquid-phase precipitation, physical adsorption and two times of reduction is adopted, and the compact spherical nickel powder which is even in grain size distribution is prepared. In addition, the grain size and density can be controlled through the nickel powder preparation method. The technical process is simple, equipment investment is small, the cost is low, and the nickel powder preparation method is suitable for industrial production. The nickel powder prepared through the nickel powder preparation method meets the requirements of 3D printing metal powder and powder metallurgy.