The nanocrystalline/amorphous NdMg11Ni + x wt.% Ni (x = 100, 200) composite hydrogen storage alloys were synthesized by ball milling, and the effects of Ni content and milling time on the hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The results reveal that the variation of the Ni content has a slight effect on the thermodynamic properties of the alloys, but it significantly improves their absorption and desorption kinetics performance. The variation of the milling time clearly affects the hydrogen storage properties of the alloys. Hydrogen absorption capacity and hydrogen absorption saturation ratio have maximum values with milling time varying. But hydrogen desorption ratio always increases with milling time prolonging. It is found that the hydrogen desorption activation energy of the alloys clearly decreases with increasing Ni content and milling time, which is responsible for the improved hydrogen desorption kinetics of the alloys. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.