The invention belongs to the technical field of lithium ion battery materials and discloses a water washing and tin coating combined modified lithium ion battery high-nickel anode material and a preparation method thereof. The preparation method includes following steps: (1), adding a high-nickel anode material into water, quickly stirring and washing for 1-20min at a rotating speed of 500-2000r/min, filtering, and drying to obtain a water-washed high-nickel anode material; (2), mixing the water-washed high-nickel anode material with a tin source well, heating to 300-700 DEG C in an oxygen-containing atmosphere at a heating rate of 1-3 DEG C/min, sintering at constant temperature for 3-10h, discharging, and breaking to obtain the modified lithium ion battery high-nickel anode material. According to the method, the high-nickel anode material is quickly washed in the water, the tin source is utilized to absorb residual lithium, and a composite coating layer of lithium stannate and tin oxide is formed on the surface of the material, so that discharging capacity and first effect of a battery are improved, and circulating performance and safety performance are improved.