In this study, the correlation between surface vanadium species and reactive lattice oxygen in the selective catalytic reduction of NO_x by NH₃ was investigated. The properties of the V/TiO₂ catalysts were investigated using physicochemical measurements, including Brunauer–Emmett–Teller surface area, temperature programmed reduction with hydrogen, Raman spectroscopy, and UV–visible diffuse reflectance spectroscopy. V/TiO₂ catalysts were prepared using the wet impregnation method by supporting 2 wt% vanadium on TiO₂ thermally treated at various calcination temperatures. Lattice oxygen participating in the reaction was found to be most abundant in 2V/TiO₂-600, prepared from TiO₂ calcined at 600°C. An increase in reactive lattice oxygen, resulting from an increase in the proportion of polymeric distorted tetrahedral structure existing on the surface of the catalyst, improved the catalyst efficiency. A polymeric distorted tetrahedral structure is referred to as a bridged bond (V–O–V). In addition, greater SO₂ resistance was related to a higher polymeric VO_x ratio. Thus, the bridged bond (V–O–V) provides the lattice oxygen participating in the reaction.