Titanium dioxide is an excellent semiconductor material with good photoelectric properties and is widely used as a photocatalyst at present. The photocatalytic mechanism of TiO₂ and its modification were introduced, the photocatalytic efficiency could be improved by means of precious metal deposition, ion doping and semiconductor composite. The applications of TiO₂ in the fields of pollutant treatment, solar cells and photocatalytic hydrogen production were introduced, which have a wide prospect.