Using the first-principles plane-wave ultrasoft pseudopotential method based on density functional theory (DFT) system, the study on titanium dioxide surface adsorption hydrogen halide gas (HX, X=F, Cl, Br) and oxygen vacancy oxidation characteristics is carried out. The calculation results show that: 1) The surface containing oxygen vacancy adsorbed hydrogen halide gas easier, whose adsorption method is chemical adsorption, among them, HF and HCl reduced by surface oxygen vacancy while HBr oxidized by surface oxygen vacancy, and the stable level of adsorption is HF>HBr>HCl; 2) adsorption hydrogen halide gas molecules can improve optical properties including dielectric constant, absorption coefficient and reflectivity of the TiO2 (110) surface, and the order of improvement ability is HF>HBr>HCl.