Abstract: Vanadyl sulfate (V^IVOSO₄) was used to prepare carbon-supported vanadium catalyst for flue gas desulfurization. The V^IVOSO₄ impregnated on activated carbon (AC) was easily oxidized into vanadium(V) sulfate phase (possibly V₂O₃(SO₄)₂) in air, which exhibited high catalytic activity toward SO₂ oxidation, thus significantly enhancing SO₂ retention on AC. Furthermore, the vanadium(V) sulfate can be decomposed upon calcination in nitrogen with optimum temperature of 500 ℃ to form vanadium(V) oxide, further improving SO₂ retention mainly due to increase in micorpore volume suitable for sulfate storage and showing suitability of vanadyl sulfate to prepare traditional V₂O₅/AC catalyst. To obtain fully oxidized vanadium oxides, preoxidation was carried out on catalyst after calcination. However, due to ablation of carbon support, reduction of vanadium and/or formation of surface oxygen groups, the preoxidation was negative for SO₂ retention. Additionally, this paper provided preliminary evidence indicating transformation of vanadium(V) oxide in V₂O₅/AC into vanadium(V) sulfate during desulfurization. Combined with catalytic role of vanadium(V) sulfate for SO₂ oxidation, SO₂ removal on V₂O₅/AC likely followed a mechanism that the vanadium(V) oxide firstly transformed into vanadium(V) sulfate and the latter was then responsible for subsequent SO₂ oxidation into H₂SO₄.