The high temperature corrosion properties of three super austenitic stainless steels 254SMo, 904L and 317L, were studied in a molten salts mixture of 30%Na₂SO₄+30%K₂SO₄+20%NaCl+20%KCl at 650, 700 and 750 ℃ for 50 h, respectively. By virtue of examination of the corrosion kinetics, composition and morphology of corrosion products, the high-temperature corrosion mechanism of three kinds of austenitic stainless steels in the molten salts' mixture was explored. The results show that all the three steels exhibit mass loss at different temperatures, and the order of corrosion resistance of the three steels can be ranked as follows: 254SMo＞904L＞317L. Molten chloride salts would accelerate the corrosion of steels and the corrosion mechanism of which may be ascribed to electrochemical corrosion and chlorine active corrosion. Sulfates dissolve and destroy the corrosion products by means of alkaline co-dissolution and thus result in serious internal and intergranular corrosion. Although all three steels are subjected simultaneously to both sulfate salt and chloride salt induced corrosion, the chloride salts are predominant in terms of the severity of corrosion. However, the addition of Mo and Ni can improve the high temperature corrosion resistance of austenitic stainless steel to a certain extent.