Abstract: Due to the closed environment with high temperature and pressure in the continuous casting (CC) process, numerical simulation technology with flexible control and low cost of phenomena in the CC mold has been a research hotspot. The multiphase flow, heat transfer, solidification of steel and slag, and other complex interaction in the mold are some of the simulation difficulties. Various physical models have been established in recent studies to obtain the reactions and effects of the different phases. However, the influence of different models on the simulation results is rarely studied. In the current study, a three-dimensional (3D) mathematical model, coupled with the large eddy simulation (LES) turbulent model and volume of fluid (VOF) multiphase model, was established to investigate the multiphase flow, slag-steel interface level fluctuation, and slag entrainment in the mold of a steel bloom CC with mold electromagnetic stirring (M-EMS). The air?slag?steel three-phase flow, slag?steel two-phase flow, and steel single-phase flow were compared. An industrial computerized tomography (CT) was used to detect the large entrainment slag inclusions in blooms with different stirring current intensities. With a 150-A current intensity and a 2-Hz frequency electromagnetic stirring at the mold, the multiphase flows are approximately identical for the three models, although different at the slag?steel interface. The speed on the top surface of the single-phase model is higher than that of the multiphase models. The level fluctuation of the two-phase model is slightly more severe than that of the three-phase model, and the net slag entrainment rates of the two-phase and three-phase models are 0.00118 and 0.00040 kg·s^?1, respectively. The turbulence kinetic energy at the slag?steel interface of the two-phase model is significantly greater than that of the three-phase model because the turbulence kinetic energy can not be dissipated, unlike that in the actual process. Thus, the predicated slag entrainment obtained by the two-phase model is higher. On increasing the stirring current intensity to 300 A, the net slag entrainment rate is 5 times and 15 times higher for the two-phase and three-phase model higher than that under 150 A; when the current frequency increases to 4 Hz, the net slag entrainment rate of the two-phase model varies little, while that of the three-phase model becomes 1/3 of that under 2 Hz. To accurately simulate and predict the slag entrainment phenomena at the CC mold, the air?slag?steel three-phase multiphase model should be mandatory.