With the exploitation and utilization of magnesite,there are fewer and fewer high-grade magnesite,while refractory quality requirements for magnesia gradually increase.The use of low-grade magnesite to produce high-purity magnesia has drawn much attention.Roasting-leaching test was conducted on a lowgrade magnesite in Haicheng to obtain leachate for providing the raw material for the subsequent preparation of high-purity magnesia.The roasting test investigated the influence of roasting grain size,time and temperature on the loss rate of magnesite.The optimum roasting conditions were particle size-2 mm,temperature 800 ℃and roasting time 40 min.Under these conditions,the loss rate of calcined magnesite was 50.85%.The ammonium chloride leaching test explored the relationship between ammonium chloride dosage,concentration,leaching time,leaching temperature,agitating speed and leaching rate.The optimal leaching conditions were determined as reagent concentration 2.5 mol/L,reagent dosage 2.5 mol/L ammonium chloride solution150 mL,leaching time 1.5