The decomposition of chlorobenzene (CB) in a non-thermal plasma (NTP) catalysis combined reactor was investigated. CoMn/TiO2 and CeMn/TiO2 were prepared using a deposition-precipitation method. CB decomposition, carbon balance, selectivity of CO2, and the byproducts of NOx and O-3 were investigated. NTP catalysis provided significantly better CB removal efficiency and CO2 selectivity than did the plasma alone. CoMn/TiO2 exhibited better removal efficiency than CeMn/TiO2 in the NTP-catalysis reactor, but the performance of the catalysts during the thermal catalytic oxidation was reversed without the NTP. To reveal the activity difference with CB decomposition in the NTP-catalysis hybrid system, the dielectric constant and the physicochemical properties of CoMn/TiO2 and CeMn/TiO2 were analyzed. The plasma, which was affected by the dielectric constant, played a dominant role in this hybrid system. The reducibility of the catalysts promoted the CO2 selectivity and O-3 decomposition. The CoMn/TiO2 was remarkably stable in the NTP-catalysis hybrid system during extended testing.