Abstract: Detailed information of the hot metal desulfurization process is very important for development of the hot metal pre-treatment technology. A comprehensive theoretical model of CaO particles desulfurization and slag regeneration process was proposed, The reacting behavior of CaO particles was described. The effects of particle size, transfer coefficient and sulfur content on the desulphurization process were invesigated. The results show that the deduced model is feasible and can be used to study the hot metal desulphurization reaction efficiently.