The effluent of sedimentation tank in water supply plant was dealt with by powdered activated carbon(PAC)-UF process,and the turbidity,CODMn,UV254,TOC and the trichloromathane formation potential of influent and effluent in PAC-UF process were measured.The results showed that the addtion of PAC could enhance the removal of particles and colloidal substances in water,which kept the turbidity of effluent lower than 0.1 NTU and the removal rate remaining above 95%.The addtion of PAC could improve the removal of organics in PAC-UF process and reduce 23.9%-31.4% trichloromethane formation potential with the optimum PAC dosage of 20-30 mg/L.It was also found that PAC could reduce membrane fouling,and the membrane fouling in PAC-UF process was mainly consist of PAC cake layer which could be easily removed by hydraulic backwashing.