The effect of the action of several impurities in different series magnesium alloys on properties of magnesium alloys are analyzed systematically in this paper . It is pointed out that the high purification of magnesium and its alloys is one of the keys in developing the use of the alloy and that it is a very difficult task . The now available high purification techniques in domestic and abroad have not satisfied the need of our Magnesium industry. It is very important for developing new techniques.