The invention relates to rare earth modified grapheme and a preparation method. The preparation method comprises the following steps of: weighing graphite oxide, purified water, a water-soluble carbon source compound, a rare earth compound and a dispersing agent respectively; adding the water-soluble carbon source compound, the rare earth compound and the dispersing agent into purified water respectively, and uniformly stirring to obtain a mixed solution; mixing the graphite oxide and the mixed solution, and uniformly stirring to obtain a paste-like precursor; and putting the paste-like precursor into a nonmetal utensil, and thermally treating the paste-like precursor by using an industrial microwave oven to prepare the rare earth modified grapheme. In the method, raw materials are rich in source, the process is easy to control, the cost is low, and the purity of a product is high; and through a performance test, the first discharge capacity is 493.5-508.6 mAh/g, and after 20 circulations, the discharge capacity is 481.6-499.8 mAh/g, so that the rare earth modified grapheme is high in electrochemical performance.