The invention provides a rear-earth surface-modified hollow glass microsphere and a preparation method thereof. The rear-earth surface-modified hollow glass microsphere is prepared from the following raw materials: hollow glass microsphere, sodium hydroxide and rare earth compound in parts by mass: 100 parts of hollow glass microsphere, 300 parts of sodium hydroxide solution and 300 parts of rare-earth aqueous solution, wherein the hollow glass microsphere has the compression strength larger than 40MPa and the average grain size of 5-80 microns, the sodium hydroxide solution has the mol concentration of 0.1-0.5 mol/l, and the rear earth is one of cerous nitrate, cerium chloride, lanthanum nitrate, lanthanum chloride, yttrium nitrate or yttrium chloride and is 0.3-2.0 percent by mass of the rare-earth aqueous solution. The preparation method comprises the following steps of: firstly, arranging the hollow glass microsphere in the low-concentration sodium hydroxide solution to increase the hydroxyl radical number and the roughness on the surface of the hollow glass microsphere; and then, adding to a rare-earth metal salt solution to modify, wash and dry. The invention has simple process, high efficiency and low cost, and the treated hollow glass microsphere is added to a polymer to remarkably improve the interfacial compatibility between a filler and a substrate, and the hollow glass microsphere modified by the method can be widely applied to the special composite material fields, such as aerospace, wind power generation, vehicles, buildings, heat insulation, sound insulation, and the like.