The reseach development of TiO2 photocatalysis technology was presented, and the mechanism of photocatalytic activity of nano-TiO2 was analyzed. Primary factors affecting the photocatalytic activity of nano-TiO2 were discussed. The smaller crystal grains are, the more effectively they can improve the photocatalytic activity of TiO2. Deposition of noble metals can promote separating efficiency of surface photo-induced current carriers and depress the electron-hole recombination. Coupling of semiconductors is...