In this paper, flameless combustion was promoted to suppress thermal-NO(x) formation in the hydrogen-high-containing fuel combustion. The PSRN model was used to model the flameless combustion in the air for four fuels: H(2)/CH(4) 60/40% (by volume), H(2)/CH(4) 40/60%, H(2)/CH(4) 20/80% and pure hydrogen. The results show that the NO(x) emissions below 30 ppmv while CO emissions are under 50 ppmv, which are coincident with the experimental data in the "clean flameless combustion" regime for all the four fuels. The simulation also reveals that CO decreases from 48 ppmv to nearly zero when the hydrogen composition varies from 40% to 100%, but the NO(x) emission is not sensitive to the hydrogen composition. In the highly diluted case, the NO(x) and CO emissions do not depend on the entrainment ratio. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.