Mg-Ce alloy was prepared by induction melting under vacuum, hydrided firstly and then Mg-Ce/Ni composite was obtained by mechanical milling Mg-Ce hydrides under Ar for 50h with addition of nano-sized Ni powder. XRD results showed CeMg12 formed in melted alloy. CeMg12 disappeared and CeH2.53 emerged during subsequent hydriding. The phase composition was not changed during ball milling process. Compared with Mg and Mg/Ni, Mg-Ce/Ni composite showed significant hydriding/dehydriding performance without any prior activation. The enthalpy of hydride formation for Mg-10.9 wt.% Ce/10 wt.% Ni composite was -70.58 kJ mol(-1) H-2. lmproved hydrogen storage properties were attributed to the catalytic effect of addition of nano-sized Ni particles and existence of CeH2.53, as well as the grain refinement, defects, etc. in the material introduced by ball milling process. (c) 2006 Elsevier B.V. All rights reserved.