A　novel　coagulation　strategy,　where　floc　property　was　regulated　by　varying　dosing　sequence　of　dual　coagulants　of　aluminum　sulfate　(AS)　and　chitosan　(CS)　with　floc　breakage,　was　applied　as　the　pre-treatment　of　ultrafiltration　to　treat　algae-laden　water.　The　river　water　(TW),　and　TW　spiked　with　intracellular　organic　matter　(IOM)　and　extracellular　organic　matter　(EOM)　respectively　(TW-IOM　and　TW-EOM)　were　tested.　The　results　indicate　that　floc　breakage　applied　in　successive　dosing　of　AS　and　CS　in　TW　and　TW-IOM　water　samples　formed　compact　flocs　through　charge　neutralization　and　bridging,　generating　dense　cake　layer　to　control　irreversible　fouling;　and　mitigated　irreversible　fouling　(R-ir)　caused　by　protein-like　and　humic-like　species　in　the　molecular　weight　(MW)　of　950-3000　Da.　For　TW-EOM　water　sample,　the　successive　addition　of　CS　and　AS　can　relieve　R-ir　by　removing　protein-like　species　and　soluble　by-products　in　the　MW　of　500-3000　Da　via　charge　neutralization,　sweeping　flocculation　and　bridging　together,　while　the　applied　breakage　aggravated　membrane　fouling.　The　obtained　results　provide　a　novel　coagulation　strategy　to　control　membrane　fouling　during　algae-laden　water　treatment.