Abstract: Electrical conductivity of molten slag is an important physicochemical property for designing the refming process in electric smelting furnaces. Though conductivities of many slag systems have been measured, the quantitative relationships of conductivity with slag composition and temperature are still very limited. In this article, the Arrhenius law was used to describe the experimental data of conductivities for CaO-MgO-Al₂O₃-SiO₂, CaO-Al₂O₃-SiO₂, CaO-MnO-AlEO₃-SiO₂, as well as CaO-MgO-MnO-Al₂O₃-SiO: systems, and it is found that activation energy can be expressed as a linear function of the content of components, where the optical basicity of slag must be within the range of 0.58 to 0.68.