The　floc　property　and　coagulation　efficiency　of　conventional　coagulation　were　compared　with　those　of　the　grading　coagulation.　In　addition,　the　parameters　including　grading　dose　interval　and　grading　dose　ratio　were　investigated.　The　results　show　that　grading　addition　not　only　reduces　the　effluent　turbidity,　but　also　increases　floc　size　and　loosens　floc　structure.　The　turbidity　of　effluent　and　floc　property　are　influenced　by　grading　dose　interval.　At　60　s　time　interval,　the　lowest　turbidity　reaches　2.06　NTU,　and　the　highest　special　growth　rate　as　well　as　the　equivalent　diameter　of　floc　achieves　49.60×10-4　s-1　and　123.0　μm,　respectively.　The　turbidity　and　floc　property　are　influenced　by　grading　dose　ratio　certainly.　When　the　grading　dose　ratio　is　4/8,　3/9,　2/10,　floc　with　looser　structure　and　larger　size　is　formed　easily.　When　the　grading　dose　ratio　is　4/8,　the　lowest　turbidity　achieves　1.81　NTU,　which　is　about　40.85%　lower　than　that　of　the　conventional　coagulation.　©　2019,　Central　South　University　Press.　All　right　reserved.