The invention relates to a lithium-rich positive electrode modified material of a lithium ion battery and a preparation method of the lithium-rich positive electrode modified material, and belongs to the technical field of a positive electrode material of the lithium ion battery. The lithium-rich positive electrode modified material comprises a positive electrode material and a three-class metal oxide cladding material, wherein the cladding material is TiO2, MnO2 or Al2O3. The preparation method comprises the steps of performing water bath stirring and heating to obtain gel by a sol-gel method, performing drying to obtain dried gel, respectively performing low-temperature pre-sintering and high-temperature calcination, obtaining the positive electrode material after cooling and grinding, dispersing the prepared positive electrode material and TiO2 and MnO2 cladding materials in deionized water, performing constant-temperature stirring, and performing standing, filtering, washing, drying and calcination to obtain the lithium-rich positive electrode modified material of the lithium ion battery. While for Al2O3, a liquid phase cladding method is adopted, the positive electrode material is dispersed in an aluminum nitrate nonahydrate solution, and the required modified material is obtained after constant-temperature stirring, standing, filtering, washing, drying and calcination. The preparation method is simple and easy to operate, the lithium-rich positive electrode modified material obtained through preparation is uniform in particle grain distribution and high in crystallinity, and the rate performance and the cycle performance of the material after cladding both are obviously improved.