It is hard to manufacture high purity,dense sintered-magnesia from natural magnesite in the prevailing process of calcining and sintering,for two reasons: a) impurity,and b) low sintering activity of coarse-grained magnesite.In this paper,95％ MgO magnesite was used as the starting material and finally magnesia of high density (3.47 g · cm-3) and high purity (98％ MgO) was obtained after the flotation purification and a three-step sintering process.An industrial scale of the beneficiation system of natural magnesite was introduced for magnesite purification.In lab experimental,the three-step sintering process was implemented by calcining,hydrating,re-calcining and sintering,which has proven the possibility of densified magnesia from natural magnesite.