Abstract: There are rich iron ore resource in Yunxi,but iron content is about 15%,belongs to low-grade magnetite,particle size is so fine that the grade of concentrate is only 51.76%,contents of Al₂O₃,SiO₂ are relatively high through three-stage grinding-weak magnetic separation.Study on reverse flotation for silicon dioxide reduction of low-grade magnetite with cationic collector,On the basis of single condition flotation technical parameters tests,Good flotation results were obtained at last With one roughing,once cleaning and twice scavenging closed-circuit process:the concentrate production rate is 63.10%,grade is 64.19%,recovery rate is 78.32%.Rate of SiO₂ reduction was 60.36%.Contents of Al₂O₃ was reduced to meet with demand of blast furnace feed.