Algal　organic　matter　(AOM),　especially　intracellular　organic　matter　(IOM),　increases　the　levels　of　color　and　taste　&　odor,　and　promotes　the　formation　of　disinfection　by-products　(DBPs).　This　study　isolated　the　IOM　from　Microcystis　aeruginosa　into　the　fractions　with　different　molecular　weight　(MW),　i.e.,　＞100　kDa,　30-100　kDa,　10-30　kDa,　and　3-10　kDa,　and　characterized　them　by　techniques　of　dissolved　organic　carbon　(DOC),　UV　absorbance　and　Excitation-emission　matrix　(EEM)　fluorescence　spectroscopy.　After　that,　the　removal　efficiency　of　these　IOM　fractions　by　aluminum　sulfate　(Al-2(SO4)(3),　alum)　at　different　Al　doses　and　pH　were　compared.　The　removal　efficiency　of　IOM,　as　indicated　by　DOC,　UV254,　and　OD680,　increased　consistently　with　higher　Al　doses,　and　the　maximum　removal　was　determined　to　be　99.7%　for　OD680,　51.4%　for　UV254,　and　38.7%　for　DOC　by　alum　at　5　mg/L.　pH　also　showed　effects,　and　the　maximum　removal　was　achieved　at　pH　6.5　with　the　maximum　removal　of　42.3%　for　DOC　and　61.5%　for　UV254.　The　higher　UV254　removal　as　compared　to　that　of　DOC　indicated　the　superiority　of　alum　to　remove　the　aromatic　IOM　species.　EEM　spectra　indicated　the　higher　protein　content　within　these　IOM　fractions,　and　the　formation　of　complexes　between　Al　and　proteins　involved　in　their　removal.　IOM　with　higher　MW　showed　more　significant　removal　of　both　DOC　and　UV254　than　that　with　lower　MW,　and　the　sweep　flocculation　mechanism　played　an　important　role.　Alum　coagulation　is　effective　and　available　for　IOM　removal　in　case　of　algae　bloom　and　minimize　its　adverse　effects　on　water　safety　thereafter.　(C)　2017　Published　by　Elsevier　B.V.