Sulfuric acid was used to decompose low-grade ascharite.After filtering the acidolysis solution, residue and the leaching solution were obtained.Boric acid was precipitated from the leaching solution at low temperature.Crystal boric acid and mother liquor were obtained by solid-liquid separation.Magnesium sulfate was recovered from the mother liquor at high temperature.X-ray diffraction pattern show that magnesium sulfate was precipitated as the form of magnesium sulfate monohydrate.