Abstract: P92 steel under different tensile stresses (0-120 MPa) was oxidized in air at 650 ℃ for different time (0-400 h), and then the oxidation kinetic curves of the steel were obtained. The morphology and phase composition of the oxidation layer on the steel surface were also analyzed. The results show that under different tensile stresses, the oxidation layers at the surface of samples mainly consisted of FeCr2O4, MnCr2O4, Cr2O3 and Fe2O3. The thickness of oxidation layer increased with the prolongation of oxidation time and the thickness increase rate increased with the increase of tensile stress. During the initial oxidation period, the oxidation layer thicknesses at the samples surface under different tensile stresses were lower than those without tensile stress while larger than those without tensile stress for the oxidation time over 80 h, and increased continuously with the increase of tensile stress. After oxidation for 400 h, the oxidation layer on the sample surface was dense with the tensile stress less than 80 MPa, and the cracks were observed while the tensile stress reached 120 MPa.