The desulfurization experiment of an Al₂O₃-CaO base pre-molten refining slag containing SrO was carried out. Experimental samples were made from industrial materials. In order to predict the slag's desulfurization ability, sulphur capacity was calculated by means of optical basicity, and there is consistency between calculated results and experimental data. A mathematical model between components and sulphur partition ratio was established with the experimental data. Based on the regression equation,the effects of single and interactive components on sulphur partition ratio were discussed. The results show that the sulphur capacity and distribution ratio decrease with the increment of Al₂O₃/CaO. SrO and MgO can increase the sulphur partition ratio. The best content of SrO in the slag should not be more than 10%, and the MgO content should be about 8%. The effect of CaF₂ on sulphur partition ratio is not obvious, therefore the addition should be limited for environmental protection.