Optimizing the performance of commercial SCR catalyst (i.e., V2O5–WO3/TiO2) for Hg0 oxidationremained stagnant as the influence mechanism of the compositions offlue gas on Hg0 oxidation wasunclear. In this work, the mechanism of Hg0 oxidation and the influence mechanism of the compositionsofflue gas on Hg0 oxidation over V2O5–WO3/TiO2 were investigated. The reaction orders of Hg0 oxidationover V2O5–WO3/TiO2 in regard to both the concentrations of Hg0 and HCl in gas phase wereapproximately 0. Hence, Hg0 oxidation over V2O5–WO3/TiO2 primarily followed the Langmuir–Hinshelwood mechanism, and the elementary reactions of Hg0 oxidation primarily involved the physicaladsorption of Hg0, the formation of Cl* radial, and the reaction of physically adsorbed Hg0 and Cl* radial. SO2, NO, H2O, and NH3 not only restrained the Cl* radial formation but also disturbed the reaction ofphysically adsorbed Hg0 and Cl* radial. Meanwhile, the physical adsorption of Hg0 was restrained by bothH2O and NH3. Hence, Hg0 oxidation over V2O5–WO3/TiO2 was obviously restrained when SO2, NO, H2O,and NH3 were present influe gas.