The quantity of the dredged sludge with high water content produced by environmental protection dredging engineering in the Taihu Lake increases day by day， which has caused very serious secondary pollution. In order to realize the rapid dehydration and resource utilization of sludge， and the removal of the clear liquid produced by deposition as soon as possible， vacuum preloading together with adding of polymeric flocculent and dehydrating agent is used for dehydration of the dredged sludge in consideration of many drawbacks of the traditional methods for sediment dumping yard of dredging engineering. Blank experiments are made， and dehydration rate and water quality are determined. The experimental results indicate that the moisture content of an admixture group (i.e.dredged sludge admixing polymeric flocculent and dehydrating agent) can be reduced from 76% to 46.5% in 650 hours， and the moisture content of a blank group is only reduced to 53.4%. The dehydrating agent does not react with flocculent， sludge， organic matter and so on. The reagent has no significant effect on the water quality. The turbidity， CODMn and pH of the outflow water conform to the wastewater discharge standard, so the vacuum preloading method combined with polymeric flocculent and dehydration agent can realize the rapid dehydration and keep the outflow water quality at the same time.