Decopperization in molten steel with FeS-Na2 S slag was investigated in the laboratory. It was found that with an increase in FeS content of the FeS-Na2 S slag, the decopperization ratio increased. The decopperization ratio could reach the maximum of 71.6% in hot metal. The decopperization ratio was closely related to the carbon content, and the higher the carbon content, the higher was the decopperization ratio. Sulphur addition was found in the process of decopperization, and the increase in sulphur content of molten steel was about 0. 2%-0. 42%. However, by adding 30%-50% of BaO to the FeS-Na2 S slag, the addition of sulfur content in molten steel could be reduced by about 50%. The finer slag system composition was FeS ： NazS ： BaO=40 ： 20 ： 40.
