On the basis of the practical production of non-oriented silicon steel, the formation of Mg O·Al2O3 inclusions was analyzed in the process of “basic oxygen furnace(BOF) → RH → compact strip production(CSP)”. The thermodynamic and kinetic conditions of the formation of Mg O·Al2O3 inclusions were discussed, and the behavior of slag entrapment in molten steel during RH refining was simulated by computational fluid dynamics(CFD) software. The results showed that the Mg O/Al2O3 mass ratio was in the range from 0.005 to 0.017 and that Mg O·Al2O3 inclusions were not observed before the RH refining process. In contrast, the Mg O/Al2O3 mass ratio was in the range from 0.30 to 0.50, and the percentage of Mg O·Al2O3 spinel inclusions reached 58.4% of the total inclusions after the RH refining process. The compositions of the slag were similar to those of the inclusions; furthermore, the critical velocity of slag entrapment was calculated to be 0.45 m·s-1 at an argon flow rate of 698 L·min-1, as simulated using CFD software. When the test steel was in equilibrium with the slag, [Mg] was 0.00024wt%–0.00028wt% and [Al]s was 0.31wt%–0.37wt%; these concentrations were theoretically calculated to fall within the Mg O·Al2O3formation zone, thereby leading to the formation of Mg O·Al2O3 inclusions in the steel. Thus, the formation of Mg O·Al2O3 inclusions would be inhibited by reducing the quantity of slag entrapment, controlling the roughing slag during casting, and controlling the composition of the slag and the Mg O content in the ladle refractory. On the basis of the practical production of non-oriented silicon steel, the formation of MgO · Al2O3 inclusions was analyzed in the process of “basic oxygen furnace (BOF) → RH → compact strip production (CSP)”. The thermodynamic and kinetic conditions of the formation of Mg O · Al2O3 inclusions were discussed, and the behavior of slag entrapment in molten steel during RH refining was simulated by computational fluid dynamics (CFD) software. The results showed that the Mg O / Al2O3 mass ratio was in the range from 0.005 to 0.017 and that MgO · Al 2 O 3 inclusions were not observed before the RH refining process. In contrast, the MgO / Al 2 O 3 mass ratio was in the range from 0.30 to 0.50, and the percentage of MgO · Al 2 O 3 spinel inclusions reached 58.4% of the total inclusions after the RH refining process. The compositions of the slag were similar to those of the inclusions; furthermore, the critical velocity of slag entrapment was calculated to be 0.45 m · s-1 at an argon flow rate of 698 L min-1, as simulated using CFD software. When the test steel was in equilibrium with the slag, [Mg] was 0.00024 wt% -0.00028 wt% and [Al] s was 0.31 wt% -0.37 wt%; these concentrations were theoretically Thus, the formation of MgO · Al2O3 inclusions would be inhibited by reducing the quantity of slag entrapment, controlling the roughing slag during casting, and controlling the composition of the slag and the Mg O content in the ladle refractory.