The separation process of non-metallic inclusions at the steel–slag interface was simulated by physical modeling. Three different kinds of particles(octahedral, plate-like, and spherical) and three different oils(kerosene, bean oil, and pump oil) were used to model inclusions and slags, respectively. The effects of inclusion geometry(shape and size) and slag properties(viscosity and interfacial tension) on the separation process were investigated. The results revealed that the variation of surface free energy and the viscosity of the slag are two significant factors affecting the separation process of inclusions at the steel–slag interface. The variation of surface free energy helped inclusions enter the slag phase, whereas the decrease of slag viscosity shortened the separation time. The deformation of the steel–slag interface could give rise to the resistance force, which would resist inclusions passing through the interface. A liquid film formed on the inclusion as it passed through the steel–slag interface, which might be related to the inclusion’s shape. The separation process of non-metallic inclusions at the steel-slag interfaces was simulated by physical modeling. Three different kinds of particles (octahedral, plate-like, and spherical) and three different oils (kerosene, bean oil, and pump oil) were The effects of inclusion inclusions (shape and size) and slag properties (viscosity and interfacial tension) on the separation process were investigated. The results of that variation of surface free energy and the viscosity of the slag of two significant factors affecting the separation process of inclusions at the steel-slag interface. The variation of surface free energy driven inclusions enter the slag phase, while the decrease of slag viscosity shortened the separation time. The deformation of the steel-slag interface could give rise to the resistance force, which would would resist inclusions passing through the interface. A liquid film formed on the inclusion as it passed t hrough the steel-slag interface, which might be related to the inclusion’s shape.