Abstract: The effects of 5% Al and 10% Al on the sulfidation behaviour of the Fe-25Cr alloy in H₂S-H₂ gas mixtures in the temperature range of 700~900℃ has been studied.The sulfidation resistance of Fe-25Cr was improved and sulfide scale morphologies,composition and structure of Fe-25Cr were changed remarkably.The sulfidation kinetics of the alloys with aluminium obeyed basically the parabolic law after an initial period of reaction time.The sulfidation mechanism of the Fe-Cr-Al alloy has been proposed.