We prepared Pd-capped Mg thin films by direct current (DC) magnetron sputtering. We investigated their structural, optical and electrical properties, as well as the effect of annealing on these films during hydrogenation and dehydrogenation. The hydrogen absorption behaviors at both room temperature and 353 K, and dehydrogenation at 353 K, were studied. The Mg film annealed at 473 K for 2 h exhibited the best absorption kinetics and superior switchable mirror proper-ties among all the samples annealed at different temperatures. We concluded that annealing temperature is a crucial parameter in forming high-quality Mg films. The improved hydriding kinetics can be attributed to the favorable morphology and structure induced by the annealing process. (c) 2008 International Association for Hydrogen Energy, Published by Elsevier Ltd. All rights reserved.