The effects of hydrogen addition and turbulence intensity on the natural gas-air turbulent combustion were studied experimentally using a constant volume vessel. Turbulence was generated by injecting the high-pressure fuel into the vessel. Flame propagation images and combustion characteristics via pressure-derived parameters were analyzed at various hydrogen volumetric fractions (from 0% to 40%) and the overall equivalence ratios of 0.6, 0.8 and 1.0. The results showed that the turbulent combustion rate increased remarkably with the increase of hydrogen fraction in fuel blends when hydrogen fraction is over 11%. Combustion rate was increased remarkably with the introduction of turbulence in the bomb and decreased with the decrease of turbulence intensity. The lean flammability limit of natural gas-air turbulent combustion can be extended with increasing hydrogen fraction addition. Maximum pressure and maximum rate of pressure rise increased while combustion duration decreased monotonically with the increase of hydrogen fraction in fuel blends. The sensitivity of natural gas/hydrogen hybrid fuel to the variation of turbulence intensity was decreased while increasing the hydrogen addition. Maximum pressure and maximum rate of pressure rise increased while combustion duration decreased with the increase of turbulent intensity at stoichiometric and lean-burn conditions. However, slight influence on combustion characteristics was presented with variation of hydrogen fraction at the stoichiometric equivalence ratio with and without the turbulence in the bomb. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.