Abstract: To address the issue of red rust defects in GPa-grade automotive steel alloyed with Si and Mn during industrial production, the oxidation behavior of 0.2C-1.5Si-2.3Mn automotive steel was systematically investigated. Samples were obtained from actual slabs produced on a MCCR line and analyzed under high-temperature conditions ranging from 900 ℃ to 1 250 ℃. This study primarily aimed to explore the mechanisms by which Si and Mn influence the structure, interfacial morphology, and elemental migration of the oxide scale. The results reveal that the oxidation behavior is significantly dependent on temperature. Below 1 000 ℃, the oxide scale predominantly consists of Fe₃O₄ and Fe₂O₃, while a layer enriched with SiO₂ and Fe₂SiO₄ forms at the interface between the oxide layer and the substrate, exhibiting lower oxidation levels within the matrix. As the temperature increases to 1 150 ℃, partial liquefaction of the interfacial Fe₂SiO₄ occurs, leading to the emergence of dispersed SiO₂-MnO composite oxides within the inner oxide layer. At temperatures exceeding 1 200 ℃, the manganese element diffuses significantly outward, resulting in the formation of a dense and brittle (Fe, Mn)₃O₄ spinel solid solution. Concurrently, the olivine phase at the interface transforms into (Fe, Mn)₂SiO₄, creating a network eutectic structure with SiO₂. This eutectic phase intrudes along the grain boundaries of FeO within the oxide scale, anchoring tightly to the steel matrix. Together with the brittle spinel phase, it exacerbates the risk of descaling residue and rolling fractures. Measures such as increasing the casting speed of continuous casting billets, optimizing the exit temperature of tunnel furnaces, and enhancing the design of descaling nozzles effectively suppressed the formation of harmful oxide phases, significantly reducing the incidence of red rust defects. This study provides a theoretical framework for improving surface quality control in short-process high-silicon, high-manganese steel production.