Based on the theoretical understanding and engineering practice,we analyze the variation characteristics of pore water pressure dissipation,settlement,physical properties and strength properties of vacuum-preloaded foundation soil,which indicates that：The value of pore water pressure dissipation is affected significantly by curving and clogging of PVD caused by disturbances of soil structure and settlement,making it do not simply decrease with the increase of the depth;The empirical coefficient of dredger fill can be a little larger,and the undisturbed soil can be a little smaller;The physical properties and the strength properties are improved obliviously,and the soil under the depth of drain boards are also improved.According to the analyzing result of the monitoring data,we discuss the effective depth and strengthening effect of vacuum preloading method,which reveals that：The effective strengthen depth of soil is affected by the value of vacuum and drainage resistance;The strengthening effect of soil within the depth range of drainage board is obvious,and that below the depth range of drainage board will reduce gradually with the depth increase and reach to no effect at last.