This research studied the involvement of mold powder and the influence of argon gas injection by means of a silicon oil-water model experiment and a 3-D numerical model. In this experiment argon gas was injected into the submerged entry nozzle through two kinds of cylinder-like porous refractory with and without wax film on inner surface. Investigation indicates that injected argon influence the involvement of silicon oil by give rise to a strong fluctuation on the interface between the water and the silicon oil layer that was used to simulate the mold powder of the continuous casting process. Silicon oil was involved more easily when the porous refractory with wax film was used than that as the porous refractory without wax film was used. This is because injected argon gas through the porous refractory with wax film produced a gas curtain inside the nozzle and in turn caused unstable water flow inside the mold and a strong fluctuation of the silicon oil-water interface. The results of experiment and numerical simulation agree with each other when gas injection rate is small. The involvement behavior of the mold powder the continuous casting process is thought to be similar to that as porous refractory with wax film was used because in both cases the wettability between the liquid and the porous refractory is poor.