Vanadium-doped anatase TiO2 was prepared by a sol-gel method while V2O5 and ethanol were used as vanadium precursors. UV-Vis transmissivity spectra revealed that the spectral response of the V-doped TiO2 shifted to the visible light region. The optimum vanadium content was 1.0% (molar fraction). Furthermore, we performed first-principles calculations on the electronic band structure of the V-doped anatase TiO2 and explained some experimental phenomena. Our results indicate that the bandgap becomes narrow and the TiO2 spectral response increases with the doping concentration increases. The valence band and the conduction band are so close that the cavities and electrons easily recombine. Additionally, strong correlation of the electron of the V 3d orbital to the Ti 3d orbital electron results in the low dispersibility of the electron on the V 3d orbital. Therefore, the photocatalytic activity of V-doped TiO2 becomes weak with the increasing of doping concentration. When the optimum phosphorus content in our calculation is 6.25% (molar fraction), the red shift of TiO2 light absorption band is the largest, which is in agreement with the experimental trend.