Abstract: Industrial experiments with three types of slags were performed to investigate the effect of slag on oxide inclusions during electroslag remelting (ESR) process. G20CrNi2Mo bearing steel was used as the consumable electrode and remelted using a 2400-kg industrial furnace. The results showed that most inclusions in the electrode were low-melting-point CaO-MgO-Al₂O₃. After ESR, all the inclusions in ingots were located outside the liquid region. When the slag consisted of 65.70wt% CaF₂, 28.58wt% Al₂O₃, and 4.42wt% CaO was used, pure Al₂O₃ were the dominant inclusions in ingot, some of which presented a clear trend of agglomeration. When the ingot was remelted by a multi-component slag with 16.83wt% CaO, a certain amount of sphere CaAl₄O₇ inclusions larger than 5 μm were generated in ingot. The slag with 8.18wt% CaO exhibited greater capacity to control the inclusion characteristics. Thermodynamic calculations indicated that the total Ca and Mg in ingots were attributed from the relics in electrode and strongly influenced by the slag composition. The formation of ingot inclusions was calculated by FactSage^TM 7.0, and the results were basically in accordance with the observed inclusions, indicating that a quasi-thermodynamic equilibrium could be obtained in the metal pool.