The invention belongs to the field of battery, and concretely discloses a preparation method of a cathode material. The preparation method comprises: performing ball-milling mixing on raw materials, wherein the raw materials comprise nickel hydroxide, manganese carbonate, and lithium hydroxide and/or lithium carbonate; and sintering at 905-995 DEG C in an oxygen-containing atmosphere, so as to obtain a metal composite oxide containing Li, Ni and Mn. The preparation method is short in synthetic route, simple and practicable, large in output, low in cost, easily controllable and free of generation of by products.