V₂O₅/TiO₂ catalysts were prepared in the presence of (NH₄)₂TiF₆ with controlled fluorine to titanium molar ratios (RF/Ti × 100) (0, 0.5, 1, 1.35 and 2) for selective catalytic reduction of nitrogen oxides (NO_x) by NH₃ (SCR process). It was found that the NO_x conversion over F-doping V₂O₅/TiO₂ was greatly improved compared with pure V₂O₅/TiO₂. The effects of F-doping on the structure of the catalysts were systematically examined using XRD, Raman spectrum, BET, TEM, H₂-TPR,NO-TPD, XPS and EPR. The XPS results showed that F ions were incorporated into the TiO₂ lattice. The high catalytic activity was ascribed to several beneficial effects produced by F-doping – preventing of grain growth, inhibiting of phase transformation from anatase to rutile, higher reducibility of good dispersion of vanadia species, creation of oxygen vacancies, and increasing active sites. It was interesting to point out that the better catalytic activity of F-doped V₂O₅/TiO₂ was achieved by the creation of surface oxygen vacancies.