The work aims to study corrosion behavior and mechanism of Super304H steel in simulated fuel gas at 650 ℃ and 700 ℃, respectively. The Super304H steel was placed in simulated fuel gas containing SO2 (volume fraction 1.5%), corrosion kinetics curves were obtained by weighting the sample at intervals. Morphology, composition and phase composition of the corrosion product at different corrosion stages were analyzed with XRD, SEM and EDS. At the initial corrosion stage, corrosion rate of Super304H steel at 700 ℃ was faster than that at 650 ℃. Continuous formation and peeling of corrosion product were observed during the corrosion process. Main constituents of the sample at the initial stage were identified as Cr2O3 and Fe2O3 at 650 ℃, then Fe3O4 was generated as the corrosion time prolonged. When the sample was corroded at 700 ℃, corrosion product peeled off more evidently. The corrosion product had a bilayer structure and it was mainly composed of Fe2O3, Cr2O3, Fe3O4 and a small amount of spinel compounds including (Ni,Cr)Fe2O4 and CuFe2O4. Sulfide formed in internal layer of the corrosion product. When Super304H steel is placed in the simulated fuel gas containing SO2 (1.5 vol%) at 650 ℃ and 700 ℃, corrosion rate accelerates as the corrosion products form and peel off continuously.