To　exam　the　effect　of　coagulation　conditions　on　organic　removal　efficiency　and　membrane　fouling　of　the　coagulation-ultrafitration　process,　Yellow　Biver　reservoir　water　was　studied　by　using　the　static　ultrafiltration　device.　Effect　of　flocculation　time　on　organic　removal,　flocs　characteristics　and　ultrafiltration　characteristics　during　the　ultrafiltration　process　was　investigated　in　this　study　and　membrane　fouling　factors　were　also　analyzed.　Results　indicate　that　the　dissolved　organic　matter　(DOC,　UV254)　removal　mainly　attributes　to　the　condensing　process,　the　following　flocculation　process　has　no　influence.　Coagulation　time　had　significant　influence　on　flocs　characteristics　and　membrane　fouling,　and　both　shorter　and　longer　time　had　negative　influence.　The　flocculation　time　of　10　mins　was　in　the　range　of　optimum,　at　which　the　fractal　dimension,　the　normalized　flux,　the　total　membrane　fouling　resistance　and　the　cake　fouling　resistance　up　to　their　minimum.　However　the　normalized　flux　decline　was　the　biggest　and　the　pore　blocking　resistance　lay　in　the　stable　state.　20　mg/L　dosage　of　PAC　and　10min　of　flocculation　time　is　the　optimal　optimum　coagulation　conditions　in　coagulation-ultrafiltration　process,　while　achieving　a　good　flocs　property　and　ultrafiltration　characteristics.　Insufficient　and　excessive　dosage　of　PAC　would　have　a　great　influence　on　coagulation,　flocs　and　cake　layer　characteristics.　©　2016,　Beijing　University　of　Technology.　All　right　reserved.