Abstract:High purity magnesium hydroxide with high purity and excellent performance was prepared by applying magnesium sulfate solution obtained from acid leaching of low-grade magnesite as raw material and ammonia as precipitant. The precipitation effect of magnesium under different conditions was investigated by changing concentration of magnesium sulfate, reaction time and temperature, ammonia concentration, aging temperature and aging time. The precipitation rate of Mg2+ is 90% above under the optimum process conditions including aging temperature of 55 ℃, aging time of 60 min, magnesium sulfate solution concentration of 1.5 mol/L, reaction time of 50 min, reaction temperature of 55 ℃, and ammonia concentration of 21%. The obtained magnesium hydroxide sample has complete crystal form, small and uniform particle size, regular spherical, with a few agglomerations. The average particle size is about 2 μm, and the purity is above 99.5%, which is higher than the requirements of industrial magnesium hydroxide Grade I product standard (HG/T 3607—2000).