In this study, to investigate the interfacial reactions among high-Mn high-Al steel, MgO-C refractory, and refining slag, a series of lab-scale experiments and thermodynamic calculations are performed. For the steel-refractory interface, we observe an interface layer composed of MgO·Al2O3 and a transition layer composed of a CaO-Al2O3 phase, along with trace MgO·Al2O3 and MgO particles. Following the interfacial reaction between the refractory and refining slag, an interface layer and an infiltration layer are detected. Subsequently, the cleanliness of high-Mn high-Al steel is investigated based on the multi-interfacial reactions. The results indicate that the evolution process of oxide inclusion follows the reaction Al2O3→MgO·Al2O3→CaO-MgO-Al2O3, with the addition of refining slag and MgO-C refractory. Additionally, a trend of aggregated AlN inclusion is observed. In certain cases, aggregated AlN inclusions are attached to the MgO·Al2O3 or CaO-MgO-Al2O3 inclusions.