The invention belongs to the field of organic functional molecule modified hydrotalcite and particularly relates to hydrotalcite of which the surface is grafted with an organophosphorus heterocyclic compound, and a preparation method of hydrotalcite. According to the method disclosed by the invention, a silane coupling agent serves as a bridging linker in supercritical carbon dioxide, and the organophosphorus heterocyclic compound is chemically grafted to the surface of hydrotalcite, wherein the silane coupling agent accounts for 0.1-50 wt% of the total weight of hydrotalcite of which the surface is grafted with organic functional molecules, the organophosphorus heterocyclic compound accounts for 0.1-50 wt%, and the balance is hydrotalcite. The hydrotalcite of which the surface is grafted with the organic functional molecules, disclosed by the invention, can serve as a functional assistant, is added into macromolecular materials, such as polyolefins, polyesters, epoxy resin, binders, coating materials, rubber or fibers, and is used for improving the thermal ageing resistance, photo-aging resistance, heat resistance, transparency, flame retardance and the like of the prepared materials.