Dissolved gas flotation (DGF) is used for removing inclusions from molten steel. The supersaturated gas forms bubbles on inclusions and carry them to the melt’s surface. Inclusion removal is modelled visually by applying a water simulation system. A mathematical model is developed to simulate the removal rate of inclusions from steel melts. From the experimental results and mathematical calculation, the mechanism of the inclusion removal by DGF was discussed, and it was concluded that first the relationship between inclusion removal efficiency and dissolved gas content, second the bubble nucleation on suspended inclusion in supersaturated molten, and finally the multi-fine bubbles flotation to the surface.