Abstract: Magnesium oxide was prepared with magnesium chloride from Qinghai Salt Lake as the primary raw material. Through dissolving，purification，and refining, the magnesium chloride was pyrolyzed by spray pyrolysis method in a vertical pyrolysis furnace to prepare magnesium oxide.Influence of temperature and feed rate on the decomposition rate of magnesium chloride was emphatically studied，and the optimum conditions were confirmed：the best pyrolysis temperature was 600 ℃ and feed rate was 12 L/h.Under the optimum conditions，the decomposition rate of magnesium chloride was more than 99%.The advantage of this method was simple，and easy to operate，therefore it′s a promising production method of magnesium oxide.

Key words: magnesium chloride, spray pyrolysis, decomposition rate, feed rate, magnesium oxide