Mg17Al12and rare earth improved Mg17Al12La0.45 alloys were prepared by resistance melting method. The hydrogen sorption properties of the alloys with and without ball-milling process were investigated with the help of PCT measurements. The phase compositions of the experimental alloys were determined through powder X-Ray diffraction. It is found that the introduction of La and the high energy ball-milling technique could remarkably improve the hydrogen sorption capability of Mg17Al12. For Mg17Al12La0.45 alloy, the hydrogen absorption starts at 473K and the hydridying rate increases at each temperature (573K, 523K, 473K) after high energy ball-milling process. The hydrogen desorption capacity of this alloy is 4wt% at 573K. XRD shows that there are two phases Mg17Al12 and Al2La0.15Mg0.85 after melting and Al2La0.15Mg0.85 phase always exists during hydrogen sorption cycles of Mg17Al12La0.45.