The　DOM　removal　efficiency　of　the　East　River　treatment　with　the　process　of　conventional　coagulation-sedimentation,　PAC　pre-adsorption　coagulation-sedimentation,　KMnO4　pre-oxidation　and　PAC　pre-adsorption　coagulation-sedimentation　was　investigated　in　terms　of　molecular　weight　distribution.　The　result　showed　that,　the　DOC　of　the　East　River　raw　water　in　flood　period　was　mainly　3000-10000　and　＞10000,　which　proportion　was　30.8%　and　43.2%,　respectively.　The　results　of　continuous　flow　dynamic　experiment　showed　that　conventional　coagulation　sedimentation　process　mainly　removed　organic　matter　which　molecular　weight　was　more　than　10000.　KMnO4　pre-oxidation　and　PAC　pre-adsorption　coagulation-sedimentation　process　could　improve　organic　matter　removal　rate　of　each　molecular　weight.　The　DOC　removal　rate　of　KMnO4　pre-oxidation　and　PAC　pre-adsorption　coagulation-sedimentation　process　was　84.0%.　The　removal　rate　raised　54.2%　compared　with　conventional　coagulation　process.　KMnO4　pre-oxidation　and　PAC　pre-adsorption　coagulation-sedimentation　process　can　enhance　the　removal　rate　of　DOM　effectively.