An Efficient utilization process of high impurity fluosilicic acid was designed and researched to produce NH₄F with co-production of MgF₂.On the basis of characteristics of high impurity fluosilicic acid and mother liquor of NH₄F,a series of key factors were deeply studied to make up for the lack of related researches,including pH,reaction temperature,free ammonia,feeding method,exothermic curve,concentration curve and material balance,etc..Optimized process conditions were obtained,under which,the yield of primary crystallization of NH₄F was about 25%,which meet the requirements of first-class products in GB/T 28653—2012;the yield of MgF₂ reached more than 95%,which meet the MF-2 requirements of YS/T 691—2009.Research on concentration revealed that there was a good linear relationship between the concentration and density of NH₄F（y=3.9778x-4.0017;y：the concentration;x：the density）,and the critical crystallization density was 1.14 g/cm³.Material balance research showed that the studied process had a high raw material utilization and important industrial application value.