Abstract: Technology for preparation of magnesium sulfate heptahydrate from dunite by acid leaching method was introduced.Influences of process conditions,such as concentration of H<SUB>2</SUB>SO<SUB>4</SUB> solution,the temperature and time of acid leaching,mineral size and stirring velocity on the dissolution of dunite and on preparation of magnesium sulfate heptahydrate were studied.Detailed processing conditions were as follows:first dunite was calcined for 4 h at 700 ℃ and treated by H<SUB>2</SUB>SO<SUB>4</SUB>solution with 4.0 mol/L at 100 ℃ for 2 h.Secondly,leaching solution was oxidized by H<SUB>2</SUB>O<SUB>2</SUB> after filtering and ammonia was added in to adjust its pH at 7.0~8.0.After impurities were leached,the leaching solution was crystallized in cold.Crystals were dried at 40～45 ℃ by heat for 2 h and coarse magnesium sulfate was obtained.Then coarse magnesium sulfate was crystallized again,and high-purity magnesium sulfate heptahydrate would be obtained.Leaching rate of Mg<SUP>2+</SUP> can reach 97.86% and the purity of product was 99.1% above under those conditions.Product could be comparable with the requirements of HG/T 2680—1995 industrial product standard.&nbsp;&nbsp; 