Abstract: The electronic structure and optical properties of the Al doped TiO₂ crystalline material is studied by density functional theory calculation method. The results show that the intrinsic TiO₂ has direct energy gap of 2.438 eV, the Al doped TiO₂has decreased direct energy gap of 2.329 eV。The intrinsic TiO₂ and the Al dopedTiO₂both have five sub-bands, but the regions that the sub-band locate has changed for the Al dopedTiO₂. The Al has introduced many new bands within the valance bands; the density of states at Fermi level has been also decreased. The Al doping is n type doping for the TiO₂ material. The s and p electrons contribute to the mobility of carriers within the bands. The dielectric absorption peak of Al doped TiO₂ locates at 320 nm, the absorption region is widened by Al doping and the absorption region has moved to long wave light area. Both systems have the similar refractive index curves under 1000nm。The refractive index of Al doped TiO₂ is decreased under 500 nm，and it is increased above 500 nm comparing with the intrinsicTiO₂。

Key words: Optoelectronics, TiO2, Al doping, Electronic structure, Optical properties