Hydrogen (H-2) is considered as a carbon-free alternative fuel. The heat release characteristics of H-2 flame as a key parameter in its combustion process are unclear. In this study, the combustion and heat release characteristics of H-2/air diffusion flame on a micro-jet array burner were experimentally and numerically investigated. It is shown that the OH distribution and flame length based on Bilger mechanism are in good agreement with the experimental results. Furthermore, the intensity and distribution of OH and heat release rate can be adjusted by the thermal power and equivalence ratio. A uniform flame with intensive heat release rate can be achieved at a thermal power of 0.1 kW. R41: H + O-2 = OH + O and R43: H + O-2 + M = HO2 + M are the main reactions with oxidizer consumption to form reactive radicals. R40: OH + H-2 = H2O H and R47: OH + OH = O + H2O with OH consumption are the main heat release reactions at the upstream and downstream of the flame. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.