The thermal stability and hydrogen storage properties of Mg-40wt%Ti0.28Cr0.50V0.22 prepared by mechanical milled for 40h under 2.0 hydrogen pressure were investigated. The experimental results showed that the composite is easily activated, and exhibits good hydrogen sorption proper-ties. It can absorb nearly 90% hydrogen of the total capacity in 1 min, and the maximum hydrogen absorption capacity reaches to 3.2, 3.5 and 4.0 wt% at 298, 368 and 548 K in 10 min, respectively. DSC measurement results showed that hydrogen desorption temperature of composite is depressed about 150 K compared with that of pure MgH2. However, if the composite was heated over 620 K, the hydrogen desorption temperature was elevated to the same temperature as that of pure MgH2 due to the re-crystallization or growth of the nano-structure Mg, although the hydrogen adsorption kinetic were not obviously affected. Therefore, It can be deduced that nano-structure Mg phase is the main reason for decreasing the hydrogen desoprtion temperature. The nano-structure Ti0.28Cr0.50V0.22 phase plays a more important role in improving hydriding kinetics of composite. (C) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.