The oxidation behavior of UNS S44400 Stainless Steel (444SS) was studied over a temperature range of 850~950℃ at various oxygen-containing atmospheres (at Po2=0.01~1atm). The oxidation kinetics of the alloys followed the parabolic-rate law in au cases and the oxidation rate constants (k(subscript p) values) increased with increasing temperature. It was found that the k(subscript p) values of the alloy were independent of oxygen pressure, indicating that the scaling behavior of the alloy exhibited an N-type semiconductor property. Based on microstructural analyses, the scales formed on the 444SS consisted mostly of Cr2O3, minor amounts of Mn1.5 Cr1.5 and MnCr2O4 TiO particles generated by internal oxidation. In addition, a small amount of TiO2 was also observed on the surface of scales at T≥900℃.