Investigations of instantaneous flame characteristics and near-wall heat transfer of syngas mixtures including H2-rich and H2-lean flames have been performed in an impinging non-premixed configuration for a Reynolds number of 2000 and a nozzle-to-plate distance of 4 jet nozzle diameters by direct numerical simulation and flamelet generated manifold chemistry. The results presented were obtained from simulations using a uniform Cartesian grid with 200 × 600 × 600 points. The spatial discretisation was carried out using a sixth-order accurate compact finite difference scheme and the discretised equations were advanced using a third-order accurate fully explicit compact-storage Runge–Kutta scheme. Results were discussed for the flame characteristics, reaction progress variable, velocity field and Nusselt number distributions. Significant differences have been found for the flame characteristics of syngas burning depending on the hydrogen, carbon monoxide, carbon dioxide and nitrogen percentages of the syngas mixture. High diffusivity in the H2-rich flame leads to form weaker vortical structures and thicker flames than those in the H2-lean flame. It has been observed that the maximum flame temperature decreases from the H2-rich to the H2-lean flames. It is also found that the maximum flame temperature occurs at the lean side of the stoichiometric mixture fraction of the syngas fuel mixtures. The composition of the syngas mixture has a significant impact on the flame characteristics of the impinging flame, including the near-wall flame structure and heat transfer.