<p>Addressing the quality defects in continuously cast high-Al steels caused by slag-metal interfacial reactions, this study pioneers investigate the mechanistic effects of electric field on interfacial reactions between CaO–SiO₂ slag systems with basicity of 0.6 and Al-containing molten steel combining ab initio molecular dynamics (AIMD) simulations and slag-metal contact experiments. The CP2K software was employed to construct a slag-metal system model, simulating the effects of various electric field conditions on interfacial reactions at 1837 K. Results demonstrated that under applied direct current (DC) electric field, the energy barrier of Si–O bonds’ first coordination shell increased with enhanced bond stability, whereas Al–O bond stability decreased significantly, hindering the formation of stable Al–O tetrahedral structures. Atomic migration trajectories revealed O ions migrating toward the anode, and Al ions drifting toward the cathode, thereby reducing Al–O bonding opportunities. Notably, tetrahedrally coordinated Al³⁺ and Si⁴⁺ ions exhibited minimal susceptibility to electric field forces. Comprehensive analysis of atomic charge variations reveals that applied electric field suppress slag-metal reactions by regulating ion migration behavior without altering interatomic bonding configurations. The slag-metal contact experiments demonstrated that reactions occurred between pre-fused CaO–SiO₂ slag with basicity of 0.6 and aluminum in metal under electric field conditions of +0.5, − 0.5, and 0 V. It is specifically reflected that the application of a +0.5 V electric field significantly reduced Al₂O₃ content in the slag compared to the control group (0 V) over time, thereby suppressing reaction progression. Conversely, the reverse electric field (− 0.5 V) enhanced Al₂O₃ formation and promoted reaction advancement, with experimental observations showing strong consistency with simulation predictions.</p>