Appropriate　mixing　conditions　are　always　favorable　during　enhanced　coagulation　for　the　desirable　performance.　However,　up　to　now,　there　are　little　studies　systematically　investigated　the　effects　of　mixing　duration　and　intensity　on　coagulation-flocculation　efficiency　based　on　a　comprehensive　consideration.　Different　mixing　intensity　and　duration　were　applied　in　coagulation　and　flocculation,　respectively,　using　aluminum　sulfate　as　the　coagulant　at　a　predetermined　dosage　where　significant　hydroxide　precipitate　occurs.　Flocs　formation,　breakage　and　regrowth　were　monitored　using　a　＇turbidity　fluctuation＇　technique,　photometric　dispersion　analyzer　(PDA)　measurement.　In　addition,　the　flocs　images　were　in　situ　captured　using　a　charged-coupled　device　camera　to　further　the　knowledge　of　flocs　characteristics,　such　as　fractal　dimension　and　settleability.　The　results　indicated　that　a　slightly　prolonged　rapid　mixing　time　(120　s)　improved　floc　density　with　better　settleability　when　the　mixing　intensity　in　coagulation　stage　was　maintained　at　a　central　level.　In　contrast,　a　little　higher　mixing　intensity　(40.2　s(-1))　in　flocculation　stage　induced　more　compact　flocs,　however,　with　smaller　homogeneous　size.　The　compensatory　interaction　of　mixing　conditions　between　coagulation　and　flocculation　stages　was　verified.　Particularly,　this　work　was　expected　to　provide　a　useful　suggestion　on　optimizing　coagulation　and　flocculation　separately,　and　thus　the　desirable　performance　can　be　obtained　by　the　optimized　operational　design.