In this paper, we studied the effect of single- and co-substitution of Ti and Fe on vacancy formation and hydrogen desorption on MgH2 (110) surface through first principles calculations. In the surface, we calculated and compared total electronic energies for all possible co-substitution systems in order to determine the preferential Ti and Fe co-substitution site. Substitution energy showed that Ti and Fe co-substitution is more energetically favourable than single-substitution of Ti or Fe in the surface. The bond length, DOS and Bader atomic charge were estimated in order to understand bonding mechanism between atoms. We also calculated formation energy for H, Mg and complex Mg-H vacancies and hydrogen desorption energies. More importantly, it was found that improvement in vacancy formation and hydrogen desorption becomes more obvious in Ti and Fe co- substitution system than single-substitution system. Our results indicated that Ti and Fe co-substitution in MgH2 (110) surface could be more effective method to improve poor hydrogen desorption properties of MgH2 than Ti or Fe single-substitution. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.