Magnesium has almost the same density, elastic modulus and strength as human bone. In fact human body contains much more magnesium than titanium. The challenge of magnesium is to improve its corrosion and biocompatibility to body fluids while it is used as implants. This paper reports the results of a study in which untreated or treated magnesium samples were subjected to cyto-compatibility tests and hemolysis tests. The results show that no the change of cells morphological or inhibitory effect on cell growth were detected in the cyto-compatibility tests. In hemolysis tests, the untreated magnesium had hemolytic effect, whereas the hemolysis of heat-treated and heatorganic filmtreated samples is within the demand (<5%). Therefore, it is very possible to use magnesium and its alloys as hard tissue substitutes if their surface is properly modified.