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热态SF6及其替代或混合气体的临界击穿场强特性是评估弧后电击穿的基础数据。基于两项近似求解Boltzmann方程的方法，得到了1个大气压下热态50%SF6-50%CF4混合气体的电子能量分布函数、折合电离反应系数和折合吸附反应系数，进而确定了混合气体的折合临界击穿场强。结果表明：在1个大气压下，当气体温度高于1800 K 时，50%SF6-50%CF4混合气体的折合临界击穿场强高于纯SF6；当温度高于2600 K时，与纯SF6和SF6-N2的情况不同，由于CF4分解物的影响，50%SF6-50%CF4混合气体的折合临界击穿场强随温度升高而增大。此外，还计算了1个大气压下不同比例冷态SF6-CF4混合气体的折合有效电离系数和折合临界击穿场强，并通过与已有结果的对比，验证了计算方法和参数的有效性。“,” The reduced critical electric field strength is an important indicator for the evaluation of dielectric breakdown of SF6 and its mixtures. The electron energy distribution function, reduced ionization coefficient and attachment coefficient of SF6-CF4 mixtures were obtained at 1atm and gas temperatures to 3000K, by two-term Boltzmann equation analysis. Then the reduced critical electric field strength could be determined. The results show that, at temperature above 1 800 K, the reduced critical electric field strength of 50%SF6-50% CF4 mixture is higher than SF6 gas; at temperature beyond 2600K, different from the cases in pure SF6 and SF6-N2 mixtures, due to the dissociation of CF4, the reduced critical electric field strength of 50%SF6-50%CF4 mixture increases with the temperature rising. In order to validate the calculation method and parameters, the reduced effective ionization coefficient and reduced critical electric field strength of SF6-CF4 mixtures under ambient temperature and 1 atm were calculated and compared with other literatures. The comparison results confirmed the validity of the presented calculation method and parameters.