Abstract: At temperature of 55~60℃ and pH=9.5~10.0,inorganic surface treatment was carried out with sodium metaaluminate for 30 nm titanium dioxide.The particle size distribution,zeta potential,UV-visible spectrum and thermal endurance of the sample before and after surface treatment were compared and analyzed.Then,optically variable car paint was prepared with aluminiumpaste and nano-titanium dioxide before and after inorganic surface treatment,and the weather resistance and optically variable performance were compared.The results show that compared with those of raw nano-TiO₂,the particle size distribution of nano-titanium dioxide after surface treatment by aluminum hydroxide is more uniform,and the zeta potential of the surface modified nano-TiO₂ changes from negative to positive value with stronger ultraviolet absorption intensity,and improved temperature resistance and weather resistance.The optically variable performance of the nano-TiO₂ does not change much by surface modification.