The acid leaching tailings of vanadium-bearing stone coal minerals (hereinafter referred to as “tailings”) is the solid waste discharged in the industry of vanadium extraction from stone coal. Using the tailings as raw materials for the preparation of ceramsite is an important way for the resource ultilization of the tailings. Ceramsite can be widely used in many areas, and the main application is to be used as lightweight aggregate in construction industry. Lightweight aggregate has a critical requirement of sulfur content when it is used as building materials. The total contents of sulfate and sulfide, calculated by SO3, should be no higher than 1.0wt%. Usually, the sulfur content (calculated by SO3) of the tailings is much higher than 1.0wt%, which is much higher than the requirement of lightweight aggregate. So, it is necessary to study the release of sulfur during the preparation of ceramsite using tailings as raw materials. In this work, simultaneous thermogravimetric–Fourier transform infrared spectrometry (TG–FT-IR) analysis were used to investigate the weight loss, the exothermic/endothermic phenomenon, and releasing of gases in the process of roasting the tailings as the raw materials for preparing ceramsite. The sulfur contents of samples prepared by roasting tailings at different temperatures were tested, their crystal phases were characterized, the Gibbs free energies of several reactions were obtained by thermodynamic calculation, and the mechanism of sulfur releasing from tailings was discussed accordingly. The results showed that sulfur-containing substances in the tailings gradually decomposed and SO2 was released with temperature increasing. Consequently, the sulfur content of samples gradually decreased with roasting temperature increasing. The sulfur content (0.44wt%) of samples obtained at 1200℃ can meet the requirements of lightweight aggregate. Intermediated phases such as wollastonite (CaSiO3) might be formed by the reaction of anhydrite and quartz in the tailings, accompanied with the releasing of SO2. SiO2, Fe2O3 and Al2O3 in tailings might be helpful for the releasing of sulfur.