The oxidation kinetics of 443NT stainless steel in simulated combustion atmosphere and humid air at high temperature were studied by adopting thermal-gravimetric analysis ( TGA).The morphology,composition and microstructure of the oxide scales were analyzed using SEM and XRD.The results show the weight gain of 443NT in simulated combustion atmosphere of CH4 at high temperature ( from 1 000℃ to 1 100℃ ) is parabolic relation to time and the oxygen content has little effect on its oxidation.In mixed gas of N2 - 18% H2O-X% O2 - 10% CO2,nodules form on the surface of 443NT at above 1 100℃ for the breakaway oxidation of Cr-depleted layer when the rich Cr2O3 scales are broken.The nodules consist of external and internal oxides.The external oxides are rich in iron and the internal oxides are composed of ( Fe,Cr)3O4 spinel.In humid air,few scales form on the surface of 443NT at less than 850℃.With increasing temperature above 900℃,the oxides consisted of Cr2O3 and FeCr2O4 can be found and thickness of oxide scales increase.