Abstract: The equilibrium solubility of magnesium chloride-ethanol-water (MgCl<SUB>2</SUB><SUP>-</SUP>C<SUB>2</SUB>H<SUB>5</SUB>OH<SUP>-</SUP>H<SUB>2</SUB>O) ternary system and the refractive index and density of saturated solution have been investigated by isothermal equilibrium method at 20 ℃.The ternary phase diagrams of MgCl<SUB>2</SUB><SUP>-</SUP>C<SUB>2</SUB>H<SUB>5</SUB>OH<SUP>-</SUP>H<SUB>2</SUB>O ternary system at 20 ℃ were drawn.The relations between the saturated solubility of MgCl<SUB>2</SUB>,refractive index and density of the saturated solution and the alcohol content in the liquid phase were evaluated by multiple linear regression analysis algorithm.The salting-out rate of MgCl<SUB>2 </SUB>solution aginst ethanol were calculated.No demixing phenomena were observed and no new compounds were found in the ternary system.A series of phase equilibrium data of MgCl<SUB>2</SUB><SUP>-</SUP>C<SUB>2</SUB>H<SUB>5</SUB>OH<SUP>-</SUP>H<SUB>2</SUB>O ternary system were given out,which not only provided basic thermodynamic data for solution chemistry,but also provided the foundation for purification and extraction of MgCl<SUB>2</SUB>.<BR>