Abstract: The investigation was done through thermodynamic analysis and orthogonal designed lab tests to determine the optimal conditions for copper removal from molten steel on the principle of vacuum metallurgy. The effects of vacuum tightness, copper removal reagents selected and their amounts, melting temperature and removing duration on the removal rate were studied. The results show that adding such reagent as either MgO or CO(NH2)2 into molten steel can remove copper obviously to the criterion w(Cu)<0.2% which most of steel grades require. However, by a comparison made for copper removal rates, CO(NH2)2 is better than MgO under the same conditions. The removal rate will increase greatly with the increase of reagent amount, removing duration and melting temperature. Copper can be cleaned out best in steel if in a 40 min removing duration 0.7% of CO(NH2)2 is used as copper removal reagent. Based on the lab test, an industrial test scheme was envisaged preliminarily.