Iodine doped nanocrystalline TiO2 photocatalyst was prepared by sol-gel method. The results show that crystallinity of anatase was improved upon iodine doping, and iodine not only suppressed phase transition anatase to rutile, but also exhibited an absorption in the wave length range of 400～550 nm. The photocatalytic activity of I-doped TiO2 photocatalysts（500 ℃） exceeded that of pure TiO2 photocatalyst prepared by the same method when the molar ratio of HIO3 to Ti was kept in the range of 0.05～0.20.
