The invention discloses a method for preparing a lithium nickel manganese oxide anode material. The method includes the steps that A, divalent nickel salt, divalent manganese salt and Li<+> compounds are evenly mixed and grinded, and a nickel, manganese and lithium mixture is obtained; B, persulfate with the molar weight larger than the sum of the molar weight of the divalent nickel salt and the molar weight of the divalent manganese salt and the mixture obtained in the step A are mixed and grinded, and a reaction mixture is obtained; C, the reaction mixture obtained in the step B is transferred into a polytetrafluoroethylene reaction kettle, water is added, a cover and a stainless steel reaction-kettle outer bush are arranged for sealing, the reaction temperature is controlled and kept, and reactants are obtained; D, the reactants obtained in the step C are taken out and washed with water till no sulfate radical is detected, suction filtration is carried out, and brown or black solid is obtained; E, the brown or black solid is transferred into a crucible, in the atmosphere environment, roasting is carried out, natural cooling is carried out, and the lithium nickel manganese oxide anode material is obtained. The raw materials are abundant, the price is low, environment pollution is avoided, and a brand new easy and convenient solid-liquid film phase reaction method with the easily-controlled conditions and the simple devices is adopted.