The　infiltration,　transportation　and　transformation　of　a　main　contaminant　(ammonia　nitrogen)　in　the　Taihu　Lake　sediment　through　a　clayey　soil　layer　are　studied　experimentally.　The　permeability　coefficient　and　diffusion　coefficient　under　different　pressures　are　determined　through　the　laboratory　tests　of　stimulation　test　of　infiltration　and　dynamic　soil　column　test.　The　adsorption　coefficient　of　ammonia　nitrogen　to　clay　soil　is　also　obtained　through　the　static　adsorption　test.　The　test　results　show　that　the　ammonia　nitrogen　is　mainly　adsorbed　and　obstructed　by　the　clayey　soil　layer　in　a　facility　for　the　dredged　sediments　from　Taihu　Lake.