The application of calcium peroxide (CaO2) activated with ferrous ion to stimulate the degradation of trichloroethylene (TCE) was investigated. The experimental results showed that TCE could be completely degraded in 5 min at a CaO2/Fe(II)/TCE molar ratio of 4/8/1. Probe compound tests demonstrated the presence of reactive oxygen species HO center dot and O-2(-center dot) in CaO2/Fe(II) system, while scavenging tests indicated that HO center dot was the dominant active species responsible for TCE removal, and O-2(-center dot) could promote TCE degradation in CaO2/Fe(II) system. In addition, the influences of initial solution pH and solution matrix were evaluated. It suggested that the elevation of initial solution pH suppressed TCE degradation. Cl- had significant scavenging effect on TCE removal, whereas HCO3- of high concentration showed favorable function. The influences of NO3- and SO42- could be negligible, while natural organic matter (NOM) had a negative effect on TCE removal at a relatively high concentration. The results demonstrated that the technique of CaO2 activated with ferrous ion is a highly promising technique in in situ chemical oxidation (ISCO) remediation in TCE contaminated sites. (C) 2014 Published by Elsevier B.V.