To investigate the detonation character of CHClF₂-air mixed gas,a numerical calculation method based on the theory,which the free energy is considered to be the minimum value at the equilibrium state after the reaction,was used to calculate the reaction parameters of mixed gas. The reaction temperature and pressure of the mixed gas were calculated in the different initial pressure and concentration. The results show that the reaction pressure and temperature increase along with initial pressure. The reaction temperature and pressure of mixed gas including 20 percent CHClF₂ are the maximal.