A thermally activated persulfate (PS) system was applied to degrade 1,1,1-trichloroethane (TCA) in aqueous solution. The generation of reactive oxygen species (ROS) in the system and their roles in TCA degradation were investigated. The experimental results showed that TCA (0.15 mM) could be completely oxidized in 1 h at 50 degrees C with a PS concentration of 30 mM. TCA degradation and PS decomposition well fitted a pseudo-first-order kinetic model. In addition, the chemical probe method was developed to identify the ROS. The results showed that SO4 center dot-, HO center dot, and O-2(center dot-) were all generated in the system and the generation intensities could be strengthened with the increase of PS concentration. The tests for PS persistence in solution indicated that oxidative species were intensified during the initial 2 h, suggesting more SO4 center dot- and HO were generated, whereas after 12 h SO4 center dot- and HO center dot intensities were slightly reduced. In contrast, O-2(center dot-) generated in the system was maintained at a stable level after reaction but at a slightly lower intensity simply due to quenching by PS or other species. Radical scavenger tests showed that HO center dot was the predominant radical species responsible for TCA degradation, and this was also confirmed by electron paramagnetic resonance (EPR) spectrum analysis in the system. Finally, two different pathways, dechlorination and C-C bond breakage, were proposed as the main TCA degradation mechanism. In conclusion, a thermally activated PS process is a highly promising technique for TCA degradation, and the potential to degrade highly oxidized organic contaminants greatly increases its application in in situ chemical oxidation (ISCO) remediation in contaminated sites.