Due　to　unfit　soil　and　water　conservancy　in　some　regions　of　China,　conventional　water　treatment　has　showed　some　defects　for　the　poor　quality　of　water　resource.　Ultrafiltration　(UF)　by　hollow-fiber　membranes　is　in　increasing　development　in　the　fields　of　drinking　water　purification.　Coagulation/UF　process　can　be　used　to　treat　poor　quality　surface　water:　the　permeate　quality　is　increased　and　membrane　fouling　is　reduced.　In　this　research,　a　streaming　current　detector　(SCD)　method　was　introduced　to　asses　how　coagulation　affects　membrane　performance.　Results　showed　that　membrane　performance　was　improved　with　the　coagulant　added　to　get　the　positive　streaming　current　(SC)　value,　since　with　the　positive　SC　coagulation　removed　more　organic　matters.　In　the　coagulation/UF　process,　coagulation　unit　does　not　need　to　be　controlled　to　get　complete　charge　neutralization,　the　point　of　zero　charge,　because　the　ultrafiltration　membrane　has　an　excellent　ability　to　remove　particles　and　colloids.