V+ were implanted into anantase films by metal ion implantation. The electronic band structures of TiO2 films doped with V+ were calculated using a self-consistent full-potential linearized augmented plane-wave method within the first principles formalism. Influence of implantation on TiO2 films were examined by ultraviolet-visible spectrometry. The results of experiment and calculation show that the optical band gap of TiO2 films is narrowed by ion implantation. The calculation shows that the 3d state of V+ plays a significant role in red shift of ultraviolet-visible absorbance spectrum. It was also found that the optical band gap of TiO2 films decreases, with increasing amount of V+.