Abstract: Compared with natural soft soil， dredger fill sludge has high initial moisture content (100%) and high initial void ratio, even more than three. By comparing the different relevant norms， it is indicated that the settlement calculation and the settlement value of the modified coefficients of the soft soil in design phase are inadequate to the dredger fill sludge. The settlement characteristics of the dredger fill sludge under vacuum preloading is analyzed by comparing the settlement calculation of the natural soft ground. The analysis results show that the range of the modified coefficients of the dredger fill sludge is much larger than that given in the norms. Additionally， the settlement data of the dredger fill sludge collected from different regions have been analyzed to verify the range of the settlement modified coefficients. Fitting the relationship curves between the measured settlement and thickness of the dredger fill sludge, thus it is concluded that the ratio of the settlement and thickness in 30% of the hydraulic reclamation thickness can be taken into account in the preliminary design phase.