Abstract: Heavy MgO was prepared by brucite and sodium hydroxide as raw materials.The influences of the material mix ratio and calcination temperature on bulk density，activity，and morphology of MgO products were investigated.The study found that by controlling the material mix ratio and calcination temperature，capsule shaped heavy magnesium oxide with bulk density of 1 g/mL could be prepared，which was hard by other ways.When amount-of-substance ratio of MgCl2 to NaOH was 1∶（1.2~1.8） and calcination temperature at 600~750 ℃，the prepared MgO′s bulk density could as high as 1.15 g/mL and the crystal structure stability and purity were both well.

Key words: brucite, heavy MgO, bulk density, capsule shape, crystal structure