The variation of hydrogen content in magnesium alloy scraps before and after purification treatment by Ar2 degassing and effects of hydrogen content on microstructure and mechanical properties of the alloy have been examined by self-developed quantitative hydrogen-measuring equipment for liquid magnesium and quantitative metallographic method.The results indicate that the hydrogen content in the magnesium alloy scraps can be decreased by 40% with Ar2 purification.Although the micro-porosity in the degassed scraps is reduced greatly,it is higher than that in magnesium alloy ingot at the same conditions.In addition,the density of degassed alloy is obviously improved,and the tensile strength and elongation are increased by 19% and by 63%,respectively,compared with the alloy scraps before degassing treatment.