Two lamps, including simulated sunlight lamp and UVA-365 nm lamp, were used to study the kinetics and changes of component distribution of NPEOs mixture in solution during photodegradation, as well as the effect of H2O2 on the photodegradation. LC-MS was used to analyze the products of NPEOs photodegradation. It was found that photodegradation of NPEOs occurred under both simulated sunlight and UVA irradiation, with the degradation rate being 6.20 x 10(-3) micromol/(L x h) and 1.18 x 10(-2) micromol/(L x h), respectively. The component distribution of short chain NPEO(1,3) increased during the photodegradation process under simulated sunlight, while no obvious change was observed under UVA irradiation. The presence of the oxidant, H2O2, was found to be propitious to the photodegradation of NPEOs, especially under the irradiation of simulated sunlight. At different added concentrations of H2O2, the 96 h degradation percentage of NPEOs increased from 20.9% (non-H2O2) to 44.4% (0.01 mmol/L H2O2) and even 91.5% (1.00 mmol/L H2O2), respectively. The analysis for degradation products using LC-MS suggested that CA(3-9)PEC3 might he the major photodegradation products of NPEOs, based on which the reaction mechanism of NPEOs photodegradation was speculated.