In this paper, the effect of MgO, BaO, Na 2 O and SrO addition to a pre-melted CaO-Al2O3 -Si 2 O synthetic slag on sulfur removal from plain carbon steel was studied under the same experimental conditions. The slags were pre-melted at 1400°C in an electric resistant furnace and desulfurization experiments were carried out in a high frequency induction furnace. The results showed that the optimum reaction time for desulfurization was 15 min. It was found that while SrO addition to the ternary slag enhances the sulfur removal capability, MgO, Na 2O and BaO additions reduce desulfurization efficiency of the ternary slag. Moreover, it was observed that restricting access to oxygen from the atmosphere by using a covered crucible, could increase desulfurization efficiency of the slag by more than two fold