Abstract: Corrosion tests in KCl-K₂SO₄ molten salts with different composition at different temperatures (500, 550, 600℃) were conducted on 12Cr1MoV steel. The effects of temperature and molten salt composition on corrosion kinetics, corrosion morphology and corrosion products of the tested steel were studied. The results show that with the rise of temperature or with the increase of K₂SO₄ content in molten salts, the corrosion of the tested steel increased. After corrosion in KCl-25wt%K₂SO₄ molten salt at 600℃, a large number of holes existed on surface of the tested steel and the corrosion products were granular; after corrosion in KCl-75wt%K₂SO₄ molten salt at 600℃, few holes existed on surface of the tested steel and the corrosion products were flake. The tested steel presented uneven corrosion morphology after corrosion in KCl-25wt%K₂SO₄ molten salt at 600℃ while showed uniform corrosion morphology at 550℃ and 500℃. The inner corrosion layer was composed of oxides of Fe and Cr, and the Cr content decreased with the temperature rising. The thickness of inner corrosion layer formed during corrosion in KCl-75wt%K₂SO₄ molten salt at 550℃ was 83.8 μm, nearly twice that formed in KCl-25wt%K₂SO₄ molten salt at 550℃, and the inner corrosion layer was relatively dense and the holes were relatively small.