Abstract: This paper is based all kinds of soft soil foundation monitoring results of a first-class highway.The monitoring data of the foundation surface settlement,porewater pressure,soil horizontal displacement variation rules of time and space are analyzed in detail.The results show that about 65 percents of the total settlement of foundation is due to the silt layer.The horizontal displacement of low liquid limit clay layer(under 15m) is smaller.It is related to its bigger soil intensity.Excessive fast filling velocity can make the general excessive porewater pressure above zero.Therefore close observation of the data of pore pressure is needed in surcharge preloading process in order to prevent the foundation instability.There is nearly no surface horizontal displacement at more than 30m outside the reinforced area,which has no effect on river embankment security.Combined with the monitoring data of porepressure and layered settlement,the effective influence depth of the foundation by vacuum combined surcharge preloading can reach to about 2m.