Mg-x(Ti0.9 Zr0.2 Mn1.5 Cr0.3)(x=20%, 30%, 40%) (mass fraction) composite powders were prepared by reactive ball milling with hydrogen and their hydrogen storage properties and microstructure were investigated by XRD, SEM and pressure- composition-temperature measurement. The results show that the composites have 3.83%-5.07% hydrogen capacity at 553 K and good hydrogenation kinetics, even at room temperature. Among them, the milled Mg-30%(Ti0.9Zr0.2Mn1.5Cr0.3) composite has the highest hydrogenation kinetics as it can quickly absorb 2.1% hydrogen at 373 K, 3.5% in 2 000 s at 473 K, even 3.26% in 60 s at 553 K under 3 MPa hydrogen pressure. The improved hydrogenation properties come from the catalytic effect of Ti0.9 Zr0.2 Mn1.5 Cr0.3 particles dispersed uniformly on the surface of Mg particles.