The evolution of crystal structure and chemical state of Mg1.9Al0.1Ni alloy during hydrogen absorption-desorption cycling was examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). We research the hydrogen storage capacity of the Mg1.9Al0.1Ni by the H/D kinetic curves. The HID kinetic curves indicate that the hydrogen storage capacity increased with the increased cycles and the samples were activated after 10 cycles have the maximum hydrogen storage capacity. The local structure of Ni atoms was studied by extended X-ray absorption fine structure (EXAFS). The EXAFS results indicate the Ni-Ni bonds distance has no obviously change with the cycles increasing, whereas the Ni-Mg bond lengths increase, and the Ni-Mg bond lengths are longer obviously than before 10 cycles whereas it has no obviously change after 10 cycles. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.