In order to explore the possibility of C2HF3Cl2 (R123) for the fire extinguishing agent of aircraft cargo compartment, this paper conducted experimental and theoretical research on the fire extinguishing performance and mechanism of R123, furthermore, the analogous C2HF5 (R125) was compared to explore the in-depth fire extinguishing mechanism. The minimum extinguishing concentration (MEC) of R123 in methane/air flames is 7.31 %, which is lower than 8.91 % of R125. And the experimental results reveal interesting examples of flame height and temperature changed with the addition of R123. The flame height had a phenomenon to increase first and then decrease, in comparison, the flame height kept rising with R125 adding. And the change in height reflected the addition of R123 to affect the movement of the reaction kernel, so that the temperature at different heights changed, but the temperature as a whole showed the tendence of decreasing. In addition, theoretical calculations indicated that R123 and pyrolysis products could affect the combustion reaction, such as CF3CHCl2+H=CF3CHCl+HCl, HCl + OH = Cl + H2O, CF3CH2Cl=CF3+CH2Cl, these fluorine-containing or chlorine-containing groups generated had an excellent effect on the suppression of combustion chain reactions. The in-depth experimental and theoretical study of R123 boost the development of ideal halon replacement in aircraft cargo compartment.