Mg and Mg-Ni-based hydrides were mechanically milled with TiO2 nanoparticles to prepare Mg-20 wt.% Mg2Ni0.8Cr0.2-1.5 wt.% TiO2 composite. XRD results showed that the hydrides decomposed partly during ball milling. Under the combined effects of the catalyst of TiO2 nanoparticles, Mg2Ni0.8Cr0.2 alloy and Ni particles precipitated, and the mechanical driving force, the composite showed rapid hydrogen absorption/desorption kinetics. The absorption temperatures of the composite were greatly decreased and the rates of hydriding were increased. The composite can absorb 4.6 wt.% H at 373 K within 3 min and desorb 4.33 wt.% H at 573 K within 20 min.