<p>The high-temperature compressive deformation behavior of medium manganese steel using a four-roll reversible rolling mill is investigated, revealing the effects of different Mn contents on the thermal deformation behavior of oxidation products in the alloy. It is found that within the experimental temperature range, the higher the deformation temperature, the better the plasticity of the oxidation products. It was observed that increasing the Mn content refines the grains, enhances the deformation ability of the oxidation products, and improves the flatness of the interfaces. Since (Fe, Mn)O has a similar crystal structure to FeO, the addition of Mn refines the grains of (Fe, Mn)O, causing the deformation to be distributed across more grains under the same deformation amount, and thereby improving its plasticity. At the interface between Fe–Mn alloy oxidation products and the matrix, there exists a spinel-phase solid solution, which can deform together with the oxidation products and the matrix at high temperatures. It was found that with increasing the Mn content, the size and number of pores between the spinel phases increased. First-principles simulation calculations were used to verify this, showing that Mn promotes the generation of vacancies. The greater number of pores in the spinel phase can effectively relieve the compressive stress caused by rolling deformation, thereby improving the deformation capability of the oxidation products at the interface.</p>