The conversion of H₂S on V₂O₅ in the presence of water vapor at 200 ℃ was 75%, 17% lower than that under water-free condition, which was caused by the degraded reduction of V₂O₅. The degraded reduction of V₂O₅ could be alleviated by mechnically mixing with zeolite-NaX or -KX. The conversion of H₂S on V₂O₅ mechanically mixed with zeolite-NaX or -KX was about 85%, which was 10% higher than that on unmixed V₂O₅ under the same reaction condition. However, the conversion of H₂S on V₂O₅ in presence of coal derived synthesis gas was 30%. It could be enhanced by the increase of water content. From these results, it could be concluded that the reducing power of reactants was the most important factor in the selective oxidation of H₂S and the selective oxidation of H₂S can be applied to the hot gas cleanup in IGCC system.