Abstract: The experiment of boron mud leaching technique with hydrochloric acid was studied. Its aim is to solve the problem of social and environmental problems caused by boron mud and to fully-use magnesium in the boron mud to prepare magnesium products.In the process of test，firstly，boron mud was pretreated with the method of calcination.The effects of calcination temperature and calcination time on the leaching process were investigated.The appropriate calcination technical conditions were obtained as follows：the calcination temperature was 600 ℃，and the calcination time was 2 h.In the process of boron mud leaching with hydrochloric acid，the effects of dosage of hydrochloric acid，leaching temperature，and leaching time on the leaching rate of magnesium oxide in the boron mud were studied.It also got the appropriate leaching conditions as follows： the dosage amount of HCl was 2.5 mL/g，the leaching temperature was 95 ℃，and the leaching time was 1 h.Under those conditions，the leaching rate of magnesium oxide reached 95.8%.The XRD results of leaching residue showed that forsterite and magnesite in the boron mud were completely leached.

Key words: boron mud, hydrochloric acid leaching, magnesium oxide