Photocatalysis is an emerging green environmental protection method. At present, the most studied photocatalytic material is TiO2. Due to its large band gap, the response to visible light is low, and the photo-generated electron-hole pairs are easy to recombine, which restricts the practical application of semiconductor photocatalytic materials. In order to improve the defects of TiO2 itself, this article explains the TiO2 photocatalysis mechanism and analyzes the limitations of traditional TiO2 photocatalysis. In view of these problems, it summarizes the methods of metal ion doping, noble metal modification, semiconductor recombination, and non-metal element doping. Obtained good visible light photocatalytic activity and discussed the future research and development direction of TiO2 photocatalyst.