The　efficiency　of　coagulation　and　flocculation　can　be　significantly　improved　through　floc　breakage　and　re-growth　under　appropriate　conditions.　At　low　temperature,　the　formation,　breakage,　and　re-growth　of　flocs　formed　by　kaolin　with　aluminum　sulfate　(alum＇)　were　investigated　with　PDA　2000　to　explore　the　reversibility　of　broken　flocs.　There　was　a　full　re-growth　of　flocs　when　they　were　coagulated　by　charge　neutralization;　but　when　coagulated　by　sweep　coagulation,　the　floc　break-up　process　was　distinctly　irreversible.　The　presence　of　humic　acid　in　water　facilitated　the　re-growth　of　flocs.　Proper　quantities　of　humic　acid　in　water　could　improve　the　fractal　dimension　of　flocs,　but　excessive　humic　acid　decreased　the　fractal　dimension.　The　fractal　dimension　of　flocs　after　re-growth　was　a　little　higher　than　that　before　breakage.　At　low　temperature,　humic　acid　did　not　influence　the　flocculation　index　(FI)　dramatically.　More　importantly,　the　residual　turbidity　after　re-growth　of　broken　flocs　decreased　as　the　original　coagulation　time　increased,　and　was　significantly　lower　than　that　before　floc　breakage　under　charge　neutralization　conditions,　which　could　reduce　the　dosage　of　coagulant　required　to　reach　similar　residual　turbidity.