The invention discloses a polyurethane/nanometer hydrotalcite composite with high damping, ultraviolet absorption and toughening properties and a preparation method thereof, and belongs to the field of polymer nanometer composites. The preparation process of the composite can be briefly summarized to include the following steps of conducting dodecyl sulfonate-selective intercalation on a nanometer hydrotalcite precursor, conducting grafting modification on the surface of a silane coupling agent to obtain organic modified hydrotalcite with high dispersibility, synthesizing a polyurethane prepolymer with specific isocyanato content, mixing organic hydrotalcite and polyurethane prepolymer of different contents, adding specific amounts of polyether polyol, cross-linking agents and catalysts to be polymerized in situ, and conducting film casting on a product in a template after reaction is conducted for a period of time to obtain the polyurethane/nanometer hydrotalcite composite. Compared with an ordinary polyurethane material, the prepared composite presents a better damping characteristic, higher toughness and higher ultraviolet absorption capacity, is low in cost, simple in process and excellent in comprehensive performance and has wide application prospects.