Abstract: The concentrations and distributions of nonylphenol polyethoxylates(NPnEO) and its metabolites were determined in the influents and effluents from sewage treatment plants(STPs) of four different cities in the north of China,and their concentration and distribution in the sludge from two of the STPs were also measured.Moreover,the transfer and transformation of NPnEO and its metabolites in the sewage treatment process was discussed primarily.NPnEO and its metabolites were found in all the tested samples,including the influents,effluents and sludges.NPnEO were removed to some extent in the four STPs,with the removing efficiencies ranging 23.38%～77.11% and the average efficiency being 52.86%.Large NPnEO molecules with longer ethylene oxide(EO) chain were biodegraded efficiently,however not mineralized to CO₂ but to middle metabolites,such as small NPnEO with short EO chain or nonylphenol(NP).Hence,the concentrations of NP and NP1EO and NP2EO are high in the effluents.These metabolites are of higher toxicity than their parent compounds,and exhibit endocrine disrupting activity. Hence,the process of wastewater treatment does not lead to a reduced risk but lead to an elevated risk,becoming the main source of these small NPnEO metabolites in the environment.The sludge had good capacity of adsorption of NPnEO, especially its metabolites,and the concentration of NPnEO in the sludges was high. Suitable treatment of sludges is worth further studying so as to avoid re-pollution.