Abstract: High-purity magnesia is an important chemical raw material，which has a wide application in the fields of building materials，environmental protection，agriculture，chemical catalysis，and so on.Combining with pilot experiment，preparation process of high purity magnesium oxide with salt lake magnesium chloride and lime as the raw materials was studied，and the process conditions were further optimized.The influences of pH，washing times，and aging etc.on the synthesis process of magnesium hydroxide at the room temperature were investigated.The optimum process parameters were confirmed as follows： pH was about 9.5，washed for 3 times，and the slurry without aging.This study is meaningful for guiding the industrial production of high purity magnesium oxide with magnesium chloride-lime milk method.

Key words: magnesium chloride-lime milk method, pilot test, high-purity magnesia