The invention provides a positive electrode material, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: carrying out first sintering treatment on a lithium source material and a positive electrode precursor material to obtain a first sintered product; and coating the surface of the first sintering product with a coating agent, and then carrying out second sintering treatment to obtain the positive electrode material, the coating agent being a nickel source material and / or a manganese source material. A specific coating agent is selected, a secondary sintering process (namely primary sintering, primary coating and secondary sintering) is combined to synthesize the single crystal-like positive electrode material, and the single crystal-like positive electrode material is formed by aggregating a plurality of primary particles of a single crystal-like positive electrode material with similar morphology. By adopting the preparationmethod, the synthesis process can be simplified, the energy consumption can be reduced, the yield can be improved, the washing process can be canceled, the residual lithium can be reduced, the circulating capacity is not lost, the side reaction between electrolyte and the inside of particles is reduced, the circulating retention rate is improved, and the service life of the battery is prolonged.