A nickel lithium ion battery positive electrode material having a concentration gradient, and a preparation method therefor. The material is a core-shell material having a concentration gradient, the core material is a material having a high content of nickel, and the shell material is a ternary material having a low content of nickel. The method comprises: synthesizing a material precursor having a high content of nickel by means of co-precipitation, co-precipitating a ternary material solution having a low content of nickel outside the material precursor having a high content of nickel, aging, washing, and drying to form a composite precursor in which the low nickel material coats the high nickel material, adding a lithium source, grinding, mixing, calcining, and cooling to prepare a high nickel lithium ion battery positive electrode material. The obtained material has regular morphology, uniform coating, narrow particle size distribution range, gradient distribution of the concentration of the nickel element, high content of the nickel element in the core, and low content of the nickel element in the shell; the nickel element in the core guarantees the specific capacity of the material, and the shell coating material maintains the stability of the structure of the material, so as to improve the safety of the material in the charge and discharge process, and improve the cycle and rate performance of the material.