Abstract: The molten slag belonged to the CaO-SiO₂-CaF₂-Na₂O-Al₂O₃-MgO slag system is tested in the centrifugal casting with the remelted steel water, the domestic composition of the used slag is decided from the given method. The results of the experiment show that the new slag system do not produce any pollution to the steel water for pouring, the slag lining on the ingot surface is very even and thin, its thichness is only l~2mm, the surface crackle and gas hole are prevented effectively.