The carbothermal reduction of barite is a complex multi-component and multi-phase reaction process. In this study, the HSC thermodynamic software and atomic matrix method were used to analyze the carbothermal reduction of barite. Furthermore, a systematic kinetics validation experiment was conducted. The effects of the reaction temperature, reaction time, and barite particle size on the phase composition and conversion of barite clinker into BaS were investigated experimentally. In addition, the kinetics of the carbothermal reduction process was studied using a modified kinetics model. The results indicated that 10 independent reactions occurred during the carbothermal reduction of barite. During the reduction of barite, SiO2 underwent crystal transition from the quartz phase into tridymite and cristobalite phases. Consequently, SiO2 could easily react with barium salts to form BaSiO3 and Ba2SiO4, which caused the conversion to BaS to decrease. Kinetics studies indicated that the carbothermal reduction of barite was mainly controlled by a gas-solid topochemical reaction, and the kinetics equation could be expressed using the Erofeev equation.