To resolve the regeneration problem of non-thermal plasma (NTP) reactor, the oxidation behaviors of particulate matter (PM) sampled at different engine loads were investigated using thermogravimetric analyzer. The results showed that the content of volatile organic compounds (VOC) differed great at different engine loads in raw PM but little in PM aggregation, and the percentage of the high volatile organic compounds (HVOC) in VOC increased with engine load. Little difference was observed for the oxidation behaviors of raw PM collected at different engine loads while the profiles of oxidation activity of PM aggregation moved toward left when increasing engine load. Longer time was needed to oxidize PM aggregation than raw PM. At isothermal condition, the activation energy was similar for raw PM and PM aggregation, however, the activation energy of the PM escaping from non-thermal plasma reactor was higher than that of raw PM and PM aggregation.