Abstract: The boiler heating surface corrosion and over-temperature bursting seriously affect the boiler safe operation. Especially under the background of coal quality frequent variation, frequent operation adjustment matching the grid load, the heating surface leakage often occurrence, which threatens the stable operation of the units. To investigate the corrosion behavior characteristics of steel at high temperatures, two typical convective heating surface steels T91 and Super304 H were selected to compare their corrosion behavior characteristics under air, hydrogen sulfide and sulfur dioxide three different atmospheres. It is found that the anti-high-temperature corrosion performance of Super304 H steel is significantly better than that of T91 steel. Among the three atmospheres, the ratio of average corrosion rate between T91 steel and Super304 H steel ranges from 2 to 18. The corrosion rate of both steels is the highest under hydrogen sulfide atmosphere and the lowest under sulfur dioxide atmosphere. From the appearance of corrosion products, T91 steel base after corrosion appears obvious corrugation trace, the surface is not glossy and the boundary between corrosion products is obvious. Many pore structures and the cracks can be found and the larger needle like corrosion products show a falling off trend. In contrast, the obvious corrosion trace of Super304 H steel matrix can be seen only in the atmosphere of H_2S. In the atmosphere of SO_2 and air, the surface of the matrix is still flat and the corrosion is not obvious. The line scan analysis of the corrosion products shows that the corrosion layer of T91 is mainly composed of two corrosion layers, Cr_2O_3 and Fe_2O_3. While Super304 H is composed of three corrosion layers, Cr_2O_3,NiO and Fe_2O_3. In terms of the thickness of corrosion layer, that of Super304 H is only 11.94 μm, while that of T91 is 34.8 μm. It indicates that the addition of Cr and Ni can enhance the oxidation resistance of Super304 H. Although the corrosion rates of the two steels are different, according to the oxidation resistance level of GB/T 13303—1991《Test method for oxidation resistance of steel》,the two steels, belong to the oxidation resistance type.