Lower sulfur content is absolutely necessary for high value-added quality steel, so it is required to reduce sulfur content of product in each link of metallurgical production. Sintering is one of important links to provide blast furnace raw materials. Study on Sulfur existing form in Sinter can provide significant theoretical guide on sulfur distribution in metallurgical production. In this paper, small sintering experiments were carried out and sinter samples with different alkalinities were prepared. The samples were characterized by mineralogical analysis and X-ray diffraction. The results show that Sulfur existing form in Sinter is calcium sulphide (CaS). CaS can not be oxidized and melted down in the following process of blast furnace iron-making and can directly enters into slag for discharge outside the furnace.