Abstract: Preparation methods and physicochemical properties of hexammoniated magnesium chloride were summarized. Hexammoniated magnesium chloride can be prepared by synthesis methods，such as high boiling point solvent system，water- ammonia system，low boiling point solvent system，and preparation of silane by magnesium silicide method.Applications of hexammoniated magnesium chloride were summarized in detail.Anhydrous magnesium chloride，the raw material of magnesium metal by electrolysis process，has wide applications，which can be prepared by pyrolysis with hexammoniated magnesium chloride as raw material. Hexammoniated magnesium chloride can also be used to prepare series magnesium products of high purity magnesium hydroxide，flame retardant magnesium hydroxide，basic magnesium carbonate，industrial magnesium oxide，and active magnesium oxide etc..

Key words: hexammoniated magnesium chloride, physicochemical property, anhydrous magnesium chloride