Ultrafiltration　(UF)　is　extensively　used　for　algae　removal　because　of　its　ability　to　retain　algal　cells　with　high　efficiency,　but　it　still　faces　the　problem　of　membrane　fouling　and　low　retention　capacity　of　dissolved　organics.　Hence,　a　strategy　of　coagulation　with　chitosan　quaternary　ammonium　salt　(HTCC)　enhanced　by　sodium　percarbonate　(SPC)　pre-oxidation　was　proposed　to　improve　the　UF　performance.　The　fouling　resistances　were　calculated　by　a　resistance-in-series　model　based　on　Darcy＇s　formula,　and　the　membrane　fouling　mechanism　was　evaluated　using　a　pore　plugging-cake　filtration　model.　The　effect　of　SPC-HTCC　treatment　on　the　properties　of　algal　foulants　was　explored,　and　the　result　showed　that　the　water　quality　was　improved　with　the　maximum　removal　rates　of　78.8　%,　52.4　%　and　79.5　%　for　algal　cells,　dissolved　organic　carbon　and　turbidity,　respectively.　The　SPC　could　achieve　a　mild　oxidation　effect　that　degraded　the　electronegative　organics　attached　to　algal　cells　without　destroying　the　cell　integrity,　making　the　algal　pollutants　easier　to　agglomerate　through　subsequent　HTCC　coagulation　by　forming　larger　flocs.　In　terms　of　membrane　filtration,　the　terminal　normalized　flux　was　increased　from　0.25　to　0.71,　with　the　reversible　and　irreversible　resistances　reduced　by　90.8　%　and　40.2　%,　individually.　The　synergistic　treatment　reduced　the　accumulation　of　algal　cells　and　algae-derived　organics　on　the　membrane　surface　as　inferred　from　the　interface　fouling　characteristics.　The　interfacial　free　energy　analysis　showed　that　the　synergistic　treatment　reduced　the　adhesion　of　contaminants　to　the　membrane　surface,　as　well　as　the　attraction　among　pollutants.　Overall,　the　proposed　process　has　high　application　prospects　for　algae-laden　water　purification.　©　2023　Elsevier　B.V.