Ozone is an undesirable byproduct of non-thermal plasma (NTP) for volatile organic compounds (VOCs) control. Photocatalysis combined downstream the NTP reactor and ozone was utilized to oxidize toluene. The multiple synergies Of O-3/UV/TiO2 system and the mechanism of toluene decomposition were investigated. The influence factors such as energy density, humidity and UV sources were also intensively studied. The combination of photocatalysis in the post-plasma increased the conversion of toluene and ozone to almost 80 and 90%, respectively. Water vapor played a dual role in toluene destruction and ozone removal. In total, 0.75% humidity had the best conversion of toluene and ozone at these experimental conditions. The conversion of toluene enhanced with increasing ozone removal. Among the multiple oxidation processes in the O-3/UV/TiO2 system, the O-3/TiO2 process played a key role in the decomposition of toluene. (C) 2009 Elsevier B.V. All rights reserved