The electronic structure and optical properties of the Al-doped TiO2 crystalline material is investigated by density functional theory calculation method. The results show that the intrinsic TiO2 has direct energy gap of 2.438 eV, the Al-doped TiO2 has decreased direct energy gap of 2.329 eV. The intrinsic TiO2 and the Al-doped TiO2 both have five sub-bands, but the regions that the sub-band location has changed for the Al-doped TiO2. 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 1000 nm. The refractive index of Al-doped TiO2 is decreased under 500 nm, and it is increased above 500 nm comparing with the intrinsic TiO2.