Red scale is a kind of strip surface defects which usually appear in Si-containing steels, so that it is important to study the oxidation process of Si-containting steels in order to control this defect. In the prsent study, oxidation epxeriments at different temperatures were conducted for a Si-containing steel, and the morphologies of the oxide scale in the Si-containting steel were investigated. The results show that the oxide scales of the Si-containing steel mainly consist of three layers. The outer layer is Fe2O3, the middle layer contains FeO and Fe3O4, and the inner layer is composed of of Fe2SiO4 and FeO. When the heating tmepraure is above the melting temperature of Fe2SiO4 (1173 °C), FeO distributes on Fe2SiO4 in the form of dot or lamella and Fe2SiO4 shows net-like morphology. However, when the heating temperate is below 1173 °C, no FeO is observed within Fe2SiO4 and Fe2SiO4 is blocky. In addition, the distribution of Si mainly concentrates in the inner layer and the concentration of oxigen decreases from the outer layer to the inner layer.