Autoignition suppression of hydrogen/air premixed mixtures by CF3CHFCF3(HFP) was investigated computationally. Numerical simulation was performed in isobaric and homogeneous system to evaluate the induction times. The detailed chemistry of 93 species and 817 reaction mechanism was introduced for hydrogen/air/HFP mixtures. The result of pure hydrogen/air mixture show that the resulting value of induction time depends relatively weakly on the definition used event though there are various criteria for defining the induction time such as the inflection of temperature, OH and O2 concentrations generally. Also, the autoignition temperature of H2/air mixture is estimated to about 850K, which is corresponds to the literature value. In the case of HFP addition in H2/air mixture, the results shows that there are several inflection points of radical concentration, and hence it might be to use the temperature for defining ignition delay. When HFP is added to stoichiometric H2/air mixture, the effect of ignition delay is outstanding above 10%2HFP concentration. As HFP concentration increases, both dilution and chemical effects contribute to delay the ignition. Also, the chemical effect on the ignition delay is more considerable with the higher HFP concentration. HFP . , / / (HFP) 93 817 . / , . / . HFP / OH . HFP 10%2 , , HFP .