Abstract: The high concentration of organic matter in circulating water may easily cause microbial growth and membrane fouling. Removing organic matter could improve the utilization of circulating water. The removal characteristics of dissolved organic matter in the circulating water by enhanced coagulation were investigated through conventional chemical analysis in combination with UV-visible spectra, gel filtration chromatography (GPC) and three -dimensional fluorescence. The results indicated that with the increase of FeCl₃ dosage within the range of 0-120 mg/L, the DOM removal rate went up with molecules condensation degree reduced and the molecular weight decreased. Under the condition of FeCl₃ dosage of 120 mg/L, the removal rate of TOC and SCOD were 54.06% and 59.71%, respectively; fluorescence intensity Fmax of humic substances C1, C2 and protein materials C3 were down 48.02%, 66.38% and 22.27%, respectively. Enhanced coagulation could effectively reduce the DOM in circulating water. Especially for those humic substances, which was difficult to be biodegradable, the removal effect was significant. Therefore, enhanced coagulation treatment of circulating water could be used to improve the operation stability of circulating water system and lay a good foundation for the further membrane treatment of circulating water.