Sulfur in steel is one of the most important deleterious element, so monitoring sulfur content is important to improve the quality of steel products. The solid state electrochemical principle is a selective and accurate way of measuring sulfur contend in molten metals. However, as of this date, people has not found solid sulfide electrolyte that has excellent chemical stability and high ionic conductivity, and so the strategic combinations of common solid electrolyte (such as ZrO2-based and β-alumina, etc) and sulfide auxiliary electrode have been developed to measure sulfur content indirectly. Under some conditions, it is possible to measure sulfur content using β-alumina without the need for an additional sulfide. Sulfide auxiliary electrode is generated in situ in the process of measurement of sulfur content. The approaches and materials used in the development of sulfur sensor are briefly reviewed in this paper.