Abstract: Magnesium sulfate solution can be obtained from dolomite via the processes of calcination，digestion，acid leaching，and filtration.Using NH₃·H₂O as precipitating agent，Mg（OH）₂  intermediate can be obtained and the high purity magnesium oxide was prepared through calcination.Impacts of end-point pH of dolomite slurry，reaction temperature，concentration of MgSO₄ ，and calcination temperature on the leaching and sedimentation rate of magnesium and on the purity of magnesium oxide were investigated，and the optimum processing conditions were obtained as follows：end-point pH of dolomite slurry was 6，reaction temperature was 40 ℃，concentration of MgSO₄ was 0.8 mol/L，and calcination temperature was 900 ℃.Under above conditions，the purity of magnesium oxide reached over 99.0%，which met the demand for high purity magnesium oxide.

Key words: dolomite, magnesium hydroxide, high purity magnesium oxide