In light metal hydroxide systems, hydrogen desorption generally occurs in exothermic reactions; therefore, these reactions are irreversible in principle. However, according to theoretical calculation of thermodynamics, some of these systems can desorb hydrogen in endothermic reactions. In this research, several hydroxide systems were studied to clarify the reversibility of these systems. Six types of hydroxide systems (XH + Y(OH)(n), X: Li, Na, Y: Li, Na, Mg) were prepared by ball-milling, then the desorption properties of these systems were evaluated. As a result, NaH + LiOH and NaH + NaOH systems desorbed hydrogen in endothermic reactions. Also, NaH + NaOH system absorbed hydrogen almost 100% reversibly under 300 degrees C and 1.0 MPa H-2 pressure. The reversibility in NaH + LiOH system was not accomplished in our experimental condition, because high pressure of GPa order is required for the rehydrogenation. In order to modify the desorption kinetics, we added KH catalyst to NaH + LiOH and NaH + NaOH systems. The hydrogen desorption temperature of the two systems was decreased by addition of 1 mol% of KH. The catalytic effect on hydrogen desorption properties was sustained even after the rehydrogenation of KH-added NaH + NaOH system.