Element doping is an effective way to improve the performance of hydrogen storage. The influences of Ti- and Hf-substituted dopants on the hydrogen storage and mechanical properties in a Zirconium-Cobalt alloy have been investigated by the first principle method. The results show that the Ti and Hf atoms preferentially occupy the Zr atoms to form new Zr7Co8Ti and Zr7Co8Hf compounds. The cohesive energy of Zr7Co8Ti and Zr7Co8Hf are -7.518 eV/atom and -7.531 eV/atom, thus Zr7Co8Hf shows a better structural stability than Zr7Co8Ti. The B/G ratio of Zr7Co8Ti and Zr7Co8Hf are 3.42 and 3.89, respectively, which indicates that Ti doping could increase the ductility of the alloy, thus improving the recycling performance of the alloy. The calculation for the electronic structure, mechanical property and structural stability may provide an effective way and theoretical evidence for the better design and optimization of hydrogen storage materials. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.