V2O5/WO3 TiO2 (VWT) catalysts for selective catalytic reduction (SCR) of NOx removal were prepared by a mechanical grinding method using different vanadium precursors. The SCR performances were evaluated in simulated flue gas and explained through characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, Raman sp ectroscopy, Hy temperature -programmed reduction, and in situ diffuse reflectance Fourier transform spectroscopy. VO(acac)(2)-VWT catalyst prepared using a vanadyl acetylacetonate (VO(acac)(2)) precursor exhibited the highest catalytic activity and excellent resistance to SO2 and H2O poisoning in 200-400 degrees C compared to the catalysts obtained using other precursors. The VO(acac)(2) precursor could enrich V on the surface remarkably and promote the formation and dispersion of polymeric vanadia species. Furthermore, a relatively high percentage of low-valent vanadium atoms were found on the VO(acac), VVVT surface, facilitating electron transfer between V4+ and V5+. Surfaceadsorbed.NH3 species on VO(acac)(2) VWT were much more reactive. The initial geometry of vanadium precursors determined the tendency of V to accumulate and further influenced the dispersion and final form of V species.