The invention provides a modification method of a positive electrode material. The modification method comprises the following steps: preparing lithium-rich phase powder containing lithium, nickel, cobalt, manganese and oxygen; mixing a coating material with a dispersing agent and a solvent, ultrasonically dispersing, dropwise adding into the lithium-rich phase powder, grinding to be dry, and calcining to obtain a coating product, wherein the coating material is selected from one or more of potassium hexafluorophosphate and potassium metaphosphate. The modification method comprises the following steps: performing surface modification treatment on xLi2MnO3. (1-x) LiNiyCozMn1-y-zO2 lithium-rich phase powder through potassium hexafluorophosphate and / or potassium metaphosphate, and performingin-situ decomposition on the potassium hexafluorophosphate at high temperature to form a potassium metaphosphate coating layer with a three-dimensional structure. The first coulombic efficiency, the cycling stability and the rate capability of the lithium-rich phase material subjected to surface coating treatment are all improved, so that relatively good electrochemical comprehensive performance is obtained, and the development requirements of high-power electronic equipment can be met. The preparation method of the positive electrode material is simple, wide in application range, low in costand suitable for industrial production.