Simulated　low　turbidity　and　micro-polluted　water　was　used　as　raw　water　and　aluminium　sulfate　was　used　as　coagulant,　the　flocs　growth　process,　two-dimensional　perimeter　fractal　dimension　(Dpf),　specific　surface　and　the　relationship　between　flocs　characteristics　and　coagulation　efficiency　under　three　common　coagulation　mechanisms　(charge　neutralization,　bridging　and　sweep　flocculation)　were　investigated.　The　results　indicated　that　the　highest　growth　rate　S　(0.951),　stable　flocculation　index　(FI)　value　(3.7%)　and　two-dimensional　perimeter　fractal　dimension　588)　of　flocs　were　formed　under　bridging　dominated　the　coagulation　mechanism.　Additionally,　the　flocs　stick　together　in　clumps　with　porous　space　in　such　condition　and　its　specific　surface　was　between　that　formed　by　sweep　flocculation　and　charge　neutralization　as　the　following　hierarchy:　sweep　flocculation　(83.646　m2/g)≤bridging　(98.808　m2/g)≤charge　neutralization　(116.046　m2/g).　The　FI　value,　S　and　Dpf　had　a　significant　linear　correlation　with　the　turbidity　removal　efficiency,　the　correlation　coefficient　reaching　up　to　0.979,　0.982　and　0.963,　respectively.　The　flocs　with　higher　specific　surface　and　bigger　adsorption　capacity　may　be　contributed　to　a　higher　organic　matter　removal.