A short reaction mechanism for premixed $CH_4/CHF_3/Air$ flames was developed with a reduction method of the combined application of simulation error minimization (SEM) which included connectivity method and principal component analysis. It consisted of 43 species and 403 elementary reactions at the condition of less than 5% of maximum error. The calculation time operated with a short mechanism was over 5 times faster than one with a detailed reaction mechanism. Good agreement was found between the flame speeds calculated by the short reaction mechanism and those by the detailed reaction mechanism for the entire range of $CHF_3/CH_4$ mole ratios and equivalence ratios. In addition excellent agreements were determined for the profiles of temperature, species concentration, and the production rates of the various species. So the short reaction mechanism was able to accurately predict the flame structure for premixed $CH_4/CHF_3/Air$ flames.