Preparation of magnesium fluoride

The invention relates to a manufacturing method of magnesium fluoride, which takes ammonium fluoride and magnesium chloride as raw materials and comprises the steps as follows: (1) an ammonium fluoride solution whose concentration is 30 to 45 percent and a magnesium chloride solution whose concentration is 25 to 36 percent are added in a reaction kettle at the same time for reaction, and a magnesium fluoride ground-paste is generated; (2) the obtained magnesium fluoride ground-paste is filtered to prepare a magnesium fluoride paste which is cleaned by using hot water the temperature of which ranges from 60 to 70 DEG C; the magnesium fluoride paste is dried for 1 to 2 hours at the temperature ranging from 250 to 400 DEG C after washing, and the finished product of the magnesium fluoride is obtained. The manufacturing method adopts the ammonium fluoride instead of hydrofluoric acid, wherein, the ammonium fluoride can be obtained through the ammonolysis by adding ammonia water into fluosilicic acid that is a by-product in the phosphate fertilizer industry; the fluosilicic acid is the deleterious-waste which is the by-product during the phosphate fertilizer production process, has very little purpose, and badly influences the environmental protection; in the manufacturing method, the development and the utilization of the fluosilicic acid greatly relieve the environmental protection pressure of the phosphate fertilizer production and the influences on the surrounding environment; and the cost is lower and the material is easy to get because the fluosilicic acid is the by-product in a phosphate fertilizer factory, thereby lowering the manufacturing cost of the magnesium fluoride.