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.