The synthesis of dispersions of MMA (methylmethacrylate) with different concentrations of oleic acid coated nano-TiO_2 particles was performed by hydrolysis of TiCI_4 in the mixture solutions of MMA, oleic acid and H_2O with various concentrations. When MMA: oleic acid: H_2O : TiCi_4 =1.00: 0.064 : 0.01: 0.032 (by mol fraction), the dispersion of MMA with oleic acid coated nano-TiO_2 particles was very stable. Optical absorption result showed that the absorption band was located in the ultraviolet range from 200 to 400 nm. This dispersion was added to a kind of automobile surface lustering agent (type II), and then this lustering agent with nano-TiO_2 was coated on the surface of automobile surface paint. When the doping amount of the dispersion in the lustering agent=10 vol. pct, the state of paint (color and glossiness) did not present any change after irradiation of an ultraviolet lamp with the power of 1000 watt for two days. The sample with surface paint and lustering agent doped by 10 percent dispersion after suffering from irradiation of the sunlight for half a year (from May to November) kept the original state. However, for the samples with automobile paint and lustering agent without doping of nano- TiO_2, the color and glossiness lost easily after irradiation of an ultraviolet lamp. These results prove that nano-TiO_2 is a kind of high-efficient additive of paint for protection against ultraviolet irradiation. The synthesis of dispersions of MMA (methylmethacrylate) with different concentrations of oleic acid coated nano-TiO 2 particles was performed by hydrolysis of TiCl 4 in the mixture solutions of MMA, oleic acid and H 2 O with various concentrations. When MMA: oleic acid: H 2 O: TiCi 4 = 1.00: 0.064: 0.01: 0.032 (by mol fraction), the dispersion of MMA with oleic acid coated nano-TiO 2 particles was very stable. Optical absorption result showed that the absorption band was located in the ultraviolet range from 200 to 400 nm. This doping was added to a kind of automobile surface lustering agent (type II), and then this lustering agent with nano-TiO 2 was coated on the surface of the automobile surface paint. When the doping amount of the dispersion in the lustering agent = 10 vol . pct, the state of paint (color and glossiness) did not present any change after irradiation of an ultraviolet lamp with the power of 1000 watt for two days. The sample with surface paint and lustering agent doped by 10 percent dispersion after suffering from irradiation of the sunlight for half a year (from May to November) kept the original state. However, for the samples with automobile paint and lustering agent without doping of nano-TiO_2, the color and glossiness lost easily after irradiation of an ultraviolet lamp. These results prove that nano-TiO_2 is a kind of high-efficient additive of paint for protection against ultraviolet irradiation.