Abstract: The combustion mechanisms of pure hydrogen and primary reference fuel(PRF) were coupled to build the premix laminar flame burning model for the PRF-H₂ blends on the Premix code of CHEMKIN software,followed by numerically investigating the effect of hydrogen blends on the combustion process of high octane number fuel and the mole fraction variations of main species and H,O and OH radicals.Results show that H₂ blending promotes PRF-H₂ mixtures burning velocity and accelerates the dissociation of the n-heptane and iso-octane in the PRF-H₂ mixtures. Besides,the mole fractions of H,O and OH radicals also increased with an example that the maximum mole fraction of H radical rises from 4×10^-3 to 13×10^-3 as the hydrogen energy fraction varies from 0 to 60%.