The nonisothennal dehydrogenation of TiH2 powders was studied using thermogravimetry and differential scanning calorimetry. The reaction model was established by estimating the activation energy. The results show the nonisothermal dehydrogenation occurred in a four-step process. The hydrogen released from the TiH1.5-2 phase in the first step, which led to the decrease of activation energy. The second step was derived from the formation of beta(H) in delta phase and the reaction model was Phase boundary reaction. In the third step, the hydrogen started to release from the beta(H) phase, and then the beta(H) -> alpha(H) phase transformation happened. So the activation energy E-alpha underwent a decrease followed by a quick increase. The fourth step corresponded to the formation of alpha(H) in beta(H) phase, and the slight oxidation resulted in the small fluctuation of activation energy. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.