In order to improve the hydrogen sorption kinetics of Mg at room temperature, the Mg-9.2wt%TiH1.971-3.7wt%TiH1.5 nanocomposite is successfully prepared by hydrogen plasma-metal reaction (HPMR) method and hydrogenation/dehydrogenation at 673 K. The Mg nanoparticles are hexagonal in shape with the size in the range of 50-190 nm. The spherical Ti hydrides nanoparticles of about 13 nm are uniformly dispersed on the surface of Mg nanoparticles. During hydrogenation/dehydrogenation cycle, the Ti hydrides nanoparticles restrain the growth of Mg nanopartides. The Mg-TiH1.971-TiH1.5 nanocomposite quickly absorbs 4.3 wt% H-2 in 10 min at room temperature and reaches a saturation value of 5.0 wt% in 60 min. The apparent activation energies for hydrogen absorption and desorption are 12.5 and 46.2 kJ mol(-1), respectively. The improved kinetics and reduced activation energy are explained in terms of the nanostructure of Mg and the synergic catalytic effect of TiH1.971-TiH1.5 nanoparticles. (C) 2014 Elsevier B.V. All rights reserved.