Abstract: The TiO2 thin films were prepared by electron beam evaporation with different craft parameters, and the optical property of thin film with ultraviolet (UV) irradiation were studied by using ellipsometer and spectrophotometer. The results show that the refractive index of TiO2 thin film decreases with different craft parameters after the same UV irradiation, and moreover, the variation of the index increases with the raise of the deposition rate and the substrate temperature, as well as the decline of working pressure. The transmittance of thin film declines after radiation. With the same craft parameter, the refractive index declines rapidly first and then increases along with the radiation time, however, it is always less than the initial refractive index.