A novel V2O5/CeTiOx catalyst showed excellent catalytic performance in the selective catalytic reduction (SCR) of NOx with NH3. The addition of Ti into V2O5/CeO2 enhanced catalytic activity, N-2 selectivity, and resistance against SO2 and H2O. These catalysts were also characterized by N-2 adsorption, XRD, XPS, and H-2-TPR. The lower crystallinity, more reduced species, better dispersion of surface vanadium species, and more acid sites due to the modification of V2O5/CeO2 with TiO2 all improved the NH3-SCR activity significantly. Based on in situ DRIFTS, it was concluded that the NH3-SCR reaction over V2O5/CeTiOx and V2O5/CeO2 mainly followed the Eley-Rideal mechanism.