The hydrogen desorption in Sn/MgH2 nanocomposite which is obtained by milling MgH2 with Sir has been studied. Upon formation of the nanocomposite between MgH2 and Sn, the desorption property of MgH2 was significantly improved. TPD (temperature programmed desorption), TG (thermogravimetry) and DSC (differential scanning calorimeter) measurements exhibited the existence of at least two types of hydrogen species in the Sn/MgH2 nanocomposite; the one was hydrogen in the newly formed Sn/MgH2 composite and the other hydrogen derived from MgH2 remaining in Sn/MgH2. In XRD, there were no additional diffraction peaks which suggested new phases or products resulting from ball milling of MgH2 and Sn. However, the sample after TPD measurements of Sn/MgH2, namely dehydrided sample, showed the formation of Mg2Sn with cubic structures. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.