Mg-3Ni-2MnO(2) nanocomposite is fabricated by mechanical-milling under hydrogen atmosphere, and heat transfer and mass transfer of reaction bed is measured through the self-made apparatus. The results shows that: compared to the intrinsic absorption and desorption kinetics of Mg-3Ni-2MnO(2) hydrogen storage material, the accumulated absorption and desorption kinetics of reaction bed behave so different. At the temperature range of 150 degrees C-250 degrees C during absorption process, the higher the temperature is, the better the intrinsic kinetics behave. But during the same temperature range, the lower the initial temperature of reaction bed is, the better the accumulated absorption kinetics is. During the absorption process, and the temperature of reaction bed wall is lower than center. When the reaction is finished, the reaction bed temperature turn to be homogeneous gradually. The interaction of mass transfer and heat transfer is remarkable during absorption. During desorption, it take so long time for reaction bed to discharge totally. At the initial stage of desorption, the temperature of reaction bed declines, and the center temperature falls lowest and is kept at this temperature for a long time; the higher the reaction bed temperature is, the shorter desorption time is.