Dissolved　organic　matter　(DOM)　transformation　in　sequence　batch　reactor　(SBR)　fed　with　carbon　sources　of　different　biodegradability　was　investigated.　During　the　biologic　degradation　process,　the　low　molecular　weight　(MW)　fraction　(＜　1　kDa)　gradually　decreased,　while　the　refractory　compounds　with　higher　aromaticity　were　aggregated.　Size　exclusion　chromatography　(SEC)　and　fluorescence　of　excitation　emission　matrices　(EEM)　demonstrated　that　more　biopolymers　(polysaccharides　or　proteins)　and　humic-like　substances　were　presented　in　the　extracellular　polymeric　substance　(EPS)　extracted　from　the　SBR　fed　with　sodium　acetate　or　glucose,　while　the　EPS　from　SBR　fed　with　slowly　biodegradable　dissolved　organic　carbon　(DOC)　substrate-starch　had　relatively　less　biopolymers.　Comparing　the　EfOM　in　sewage　effluent　of　three　SBRs,　the　effluent　from　SBR　fed　with　starch　is　more　aromatic.　Organic　carbon　with　MW　＞　1　kDa　as　well　as　the　hydrophobic　fraction　in　DOM　gradually　increased　with　the　carbon　sources　changing　from　sodium　acetate　to　glucose　and　starch.　The　DOC　fractionation　and　the　EEM　all　demonstrated　that　EfOM　from　the　effluent　of　the　SBR　fed　with　starch　contained　more　fulvic　acid-like　substances　comparing　with　the　SBR　fed　with　sodium　acetate　and　glucose.