In view of the characteristics of the ultra-soft newly dredged sludge, we invented the surface-layer improvement technology based on the mechanism of vacuum preloading and applied to the soft ground treatment project of reclamation land in Wenzhou. The physical and mechanical properties, particle composition, mineral composition of the sludge are analyzed. The vacuum, settlement and pore pressure were monitored in the process of vacuum preloading. The cone penetration test, sampling by boreholing and flat load test were carried out during unloading. The data show that the reinforcing effect of the soil is ideal to meet the design requirements.