Abstract: The existing problems of injection desulfurization had been analyzed.Based on the principle of KR desulfurization,the numerical simulation of rotary injection desulfurization process of injection desulfurization gun had been carried out.Through comparison,It is found out that the rotation of injection desulfurization gun can effectively reduce the splash of desulfurization process and improve the stirring of injection gas to semi-steel molten pool.On the basis of theoretical research,a new semi-steel desulfurization process based on rotary injection technology has been designed and developed in Panzhihua Iron and Steel Co.Ltd.The process has been applied to 140 t and 230 t semi-steel desulfurization convertors at Panzhihua Iron and Steel Co.and good results have been achieved.The average utilization ratio of magnesium in desulfurizer has increased from 55.46% to 68.27%,and the consumptions of splashing,iron loss and desulfurizer were reduced remarkable.The desulfurization efficiency has been improved to a certain extent.