Laminar combustion characteristics of hydrogen/air mixture diluted with N-2 + H2O are investigated based on experiments in a constant volume combustion bomb. Experiments results show that flame propagating speed and laminar combustion speed decrease significantly with N2 + H2O dilution. Flame stability increases slightly with the increase of dilution rate. It can be revealed that decrease of temperature in reaction zone leads to significant-decrease of all important elementary reactions speed. Concentration increase of dilution gas also slowed down and sometimes even reversed the direction of part of important elementary reaction. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.