Abstract: The S31035 steel was shot peened, and then the high temperature steam oxidation test was carried out at 665 ℃. The effect of shot peening on the high temperature steam oxidation behavior of the steel was studied. The results show that the unpeening sample had obvious oxide diffraction peaks after 100 h oxidation, and a double-layer of oxides was formed after 3 000 h oxidation. The oxide film thickness of the unpeening sample was about 8.07 μm. The weak (Fe,Cr)₂O₃ diffraction peak appeared in the shot peening sample after 1 000 h oxidation, and the surface oxide film was still thin after 3 000 h oxidation, with a thickness of only 0.45 μm. In oxidation, the oxidation rate constant of the shot peening sample was 3 orders of magnitude lower than that of the unpeening sample, and the steam oxidation resistance was better. The shot peening refined the surface grains, which provided more channels for chromium diffusion and led to formation of a Cr₂O₃ protective film on the surface, thereby improved the high temperature steam oxidation resistance of the steel.