Since magnesium alloy is equipped with low density, excellent die casting property and electro-magnetic shielding, it is widely applied in the automobile parts and 3C housing in Europe and USA. Industrial molten magnesium processes primarily utilize sulfur hexafluoride (SF6) as a cover gas to inhibit the surface oxidation. However the project uses CO2 Snowing as cover gas to inhibit the surface oxidation. Gottfried Wilhelm Leibniz University Hannover conducted the similar research but was not commercialized yet. The replacement of SF6 by refrigerant is under development. For example, R143a by AMC and FK(fluoric Ketone) by 3M Co. used as protection gas are both classified as HFC with short atmospheric lifetime and are easily to be decomposed into hydrofluoric acid, carbon monoxide and fluoric carbon monoxide at room temperature. The demand of SF6 for cover gas is about NT$30 million per year in Taiwan. The gradual production reduction and cost of SF6 will inevitably impose an impact on industry so that development of alternative program or technology for the existing melting furnace becomes an urgent and important strategy