The work aims to study high temperature corrosion behavior of S30432 austenitic stainless steel coated with coal-ash received from Xinyuan and Yulin power plants in 0.3% SO2 flue gas at 700 ℃. Corrosion tests were conducted by placing S30432 steel coated with coal-ash in fuel gas/coal ash. Mass change was obtained by weighting the samples at intervals during the test, and corrosion kinetics of the samples was plotted. Morphology, constituents and phase composition of the corrosion products were investigated by SEM, EDS and XRD. The S30432 steel undergone oxidation, sulfidation corrosion. The accelerated corrosion stage was observed during the corrosion test. After S30432 corroded in the coal ash with low sulfur content, no obvious corrosion product spallation was observed, a relatively compact and protective Cr2O3 film was formed on the surface of the samples, and corrosion product film was thinner. However, the corrosion products grew in layer and peeled off severely in the coal ash with high sulphur content, weight loss exceeded 45 mg/cm2 after 2000 h. The layer of corrosion products was mainly composed of Fe2O3, (Fe,Cr)2O3, NiCr2O4 and coal ash particles embedded in the corrosion layer. Cr and S-enriched corrosion layer was formed on the corrosion layer/substrate interface. Corrosion resistance of S30432 steel in flue-gas/Xinyuan coal-ash is much better than that of S30432 in flue-gas/Yuneng coal-ash. Corrosion rate of S30432 increases significantly with the increase of sulfate content in coal ash. Alloy is susceptible to hot corrosion under the synergistic effect of high temperature flue gas/coal ash. Rapid degradation of corrosion resistance of alloy is attributed to dissolution of iron, nickel, chromium and their oxides in molten salt on the surface and alloy.