A computer simulation of chemical, charged-particle, and excited-particle kinetics in a microwave post-discharge in humid air with halocarbon (CCl3F) traces has been carried out. The effect of the catalytic cycle with electrons and negative ions on the decomposition of halocarbon molecules has been studied. It has been shown that the catalytic effect increases with increasing halocarbon density, with increasing reduced electric field in the active stage of microwave discharge, and with decreasing gas pressure.