Abstract: In this paper, the mechanism of TiO₂ photocatalysis technology was described. And then the effect of particle size, defects, crystal structure, crystal morphology and surface modification were introduced. Finally, the application of TiO₂ in sewage treatment, sterilization and air purification were summarized, and the methods for promoting the photocatalytic activity of TiO₂ were overviewed, including decreasing particle size of TiO₂, increasing its defects, changing its crystal morphology, using mixed-phase and surface modification of TiO₂.