Abstract: In order to improve the quality and security of reclaimed water to reuse,ozonization is used to oxidate nonylphenol ethoxylates(NP_nEO) and nonylphenol(NP) that is one of bio-degradation products of NP_nEO,and the mechanism of the oxidation reaction is analyzed.The results show that the ozonation processes of NP_nEO mainly occur on the ethoxy chain (EO),which the EO chain of NP_nEO with various polymerization degrees has been synchronously degradated into the smaller polymerization degrees.In the 10 minutes of the reaction,the rate of a various polymerization degrees in NP_nEO mixtures meet the Poisson distribution.NP is easily to be oxidized by ozone,but incomplete.The removal rate of NP is 90% after 5 minutes of reaction.There are a lot of intermediary products to be produced in the ozonization process,which can be deduced to nonyl alcohol isomers based on the analysis of the mass spectrum of the byproducts.