Photocatalysis　or　coagulation　process　has　been　separately　studied　for　the　removal　of　natural　organic　matter　(NOM)　from　surface　water,　and　the　reaction　mechanism　of　organic　fractionations　of　treated　effluent　has　been　clarified.　Although　coagulation-based　process　has　been　extensively　studied　for　NOM　removal,　few　attempts　have　been　made　based　on　a　combined　process　that　can　not　only　efficiently　degrade　NOM,　but　also　enhance　the　coagulation　performance.　The　hypothesis　is　that　a　combination　of　photocatalysis　and　coagulation　process　in　a　single　unit　might　potentially　enhance　NOM　removal　efficiency.　This　is　because　the　nano-photocatalyst　can　serve　as　both　pre-oxidant　and　flocculation　core.　Herein,　a　combined　process　of　visible　light　photocatalysis　prior　to　coagulation　is　conducted,　with　the　transformation　efficiency　of　the　organics　fractionations　revealed.　The　as-prepared　nano-sized　photocatalyst　consisting　of　Bi2O3-TiO2　(molar　Bi/Ti　ratio　0.04:1)　had　a　stronger　visible　light　absorption　ability.　Compared　to　coagulation　alone,　the　combined　photocatalysis-coagulation　process　greatly　improved　NOM　removal,　with　synergistic　effect,　while　the　pre-photocatalysis　reduced　the　required　dosage　of　polyaluminium　chloride　(PACl)　coagulant　and　increased　the　optimal　pH　of　solution.　A　mathematical　model　optimized　by　response　surface　methodology　of　the　combined　process　was　developed　that　produced　a　good　correlation　between　predicted　and　experimental　values.　The　optimal　conditions　were　calculated　as　follow:　2.0　g/L　photocatalyst,　a　photocatalytic　reaction　time　of　10　min　18　sec,　0.04　mM　PACl　coagulant,　and　a　pH　of　4.2.　These　conditions　particularly　enhanced　removal　of　acidic　hydrophobic　substance,　humic-/protein-like　substances　and　fractions　with　molecular　weight　between　3　and　44　kDa.　The　XRD　spectra　and　SEM　images　of　the　produced　flocs　identified　that　these　flocs　consisted　of　a　core　of　photocatalyst,　which　could　contribute　to　an　effective　flocculation　and　enhanced　NOM　removal.