Two　methods　of　coagulation　and　adsorption　were　used　to　pretreat　a　simulated　micro-polluted　ground　water　to　study　the　relationship　between　ultrafiltration　(UF)　membrane　and　pollution　levels　of　different　water　samples　and　analyze　the　effect　of　particles　characteristics　on　flux　decline.　The　experimental　results　indicate　that　powdered　activated　carbon　could　reduce　the　concentration　of　organics　effectively,　but　the　effect　of　wiping　out　turbidity　is　not　obvious.　Coagulation　could　reduce　the　turbidity　of　water　effectively　although　it　has　low　efficiency　on　organics　removal.　The　coagulation　pretreatment　could　improve　the　flux　of　raw　water,　but　the　adsorption　has　no　influence　on　flux.　The　correlation　fitting　results　of　fouling　index　of　turbidity　and　dissolved　organic　matter　(DOC)　show　that　fouling　index　of　UF　has　an　obvious　correlation　with　turbidity,　but　no　obvious　correlation　could　be　found　with　DOC　concentration.　The　turbidity-causing　pollutants　are　the　major　foulant　under　experimental　condition.　The　colloidal　and　particles　sized　between　0.01　μm　and　1.2　μm　are　the　main　pollutant　which　lead　to　flux　decline,　meanwhile,　it　is　cumulatively　on　fouling　index　for　turbidity-causing　pollutants　during　UF　process.