Abstract: This article thoroughly summarized pollutant diffusion pathways of contaminated dredged material on mud dumping site, and introduced control techniques in domestic China and out side China as well. Full-scale experiments of contaminant diffusion control had been done on the mud dumping site of Taihu Wuli lake environmental dredging project, by using the clay around Taihu lake as leachate prevention material. Water quality of five points around the mud dumping site were stable during the dredging process, which showed that the clay around Taihu lake could be used as leachate prevention material. Flocculants were added to the sludge pipe, in which flocculants were mixed rapidly, then they flocculated and sedimentated on the mud dumping site. Or, the flocculants were added into the discharge outlet of the mud dumping site, which mixed quickly in the clapboard tank and flocculated in the reciprocal baffled flocculating tank, then they sedimentated in the horizontal flow sedimentation tank. The results show that the solid suspension concentration of effluent is less than ρ(SS)<200 mg/L.