Nonylphenol (NP) is a typical environmental endocrine disruptor with low concentration and high toxicity, μg/L level of NP is enough to interfere with the sex differentiation of many aquatic organisms and affect the population dynamic balance. The mechanism and pathway of NP degradation in aqueous solution by strong ionization dielectric barrier discharge were studied. The results showed that the degradation rate of NP can reach 95.2% in 60 min when the flow rate of O₃ is 5 L/min and the input voltage is 3.8 kV. Based on the electron spin resonance (ESR) results and the detection of O₃, a large amount of hydroxyl radical (·OH) and O₃ were verified. In addition, the ability of DBD method to degrade NP was also tested. The intermediate products were analyzed by liquid chromatography-mass spectrometry (LC-MS), and the degradation pathway was speculated.