Di-(2-ethylhexyl) phthalate (DEHP) is an annexing agent that is widely used in the plastics industry. Due to the endocrine-disrupting effect of this compound, the development of an efficient method for degrading DEHP is impottant. In this study, DEHP was degraded by UV-activated peroXymonosulfate (PMS) oxidation. The influences of various parameters, including PMS dose, temperature, pH, metal ions, common anions and humic acid (HA), were examined. An increase in PMS dose and the presence of metal ions and common anions was observed to accelerate the reaction, while high pH and the presence of HA inhibited the reaction. In addition, seven transformation products were identified by liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS), from which the reaction mechanism and degradation pathways were tentatively proposed. Direct oxidation, hydroxylation, cleavage of the ester bond and decarboxylation were observed in the degradation process. These findings may provide useful information for the treatment of this pollutant. (C) 2016 Elsevier B.V. All rights reserved.