A new model to study the hydriding/dehydriding （H/D） kinetic mechanism has been applied in the two-phase （α-β） region of the Mg-6mol%LaNi composite at temperature and pressure ranging from 523 to 623K and 0.256 to 0.992MPa H2. respectively. The coincidence of the theoretical calculation with the experimental data indicates that the rate-limiting step is hydrogen diffusion in the β phase for hydriding process and the diffusion of hydrogen in the α solid solution for hydrogen desorption with activation energies 89500 and 87900J/mol H2 for HID processes, respectively, which were much smaller than those of MgH2 and can be attributed to the La and Ni additions.
