Abstract: The feasibility of desulfurization by particle magnesium in hot metal pretreatment was expoundedthrough calculation in thermodynamics and dynamics. Based on 77 group data of desulfurization process in thdesulfurization station of Xuanhua Iron and Steel Group Co. Ltd., a mathematics model about desulfurization ratand magnesium utilization rate was obtained. The above model is in favor of the optimization of process iXuanhua Steel Plant and it increases the utilization rate of particle magnesium, decreases the consumption of particle magnesium, and saves the cost. To improve the desulfurization ratio of desulfurizer and utilization ratio, thtemperature of hot metal and the mass of particle magnesium should be improved, and the injection speed odesulfurizer and the blowing time should be declined.