Abstract: Based on the project about the soft-foundation treatment of Baian interchange,Gaofu road,the methods of design and construction monitoring program that are applied to reinforce soft-foundation with sand bag well are introduced systematically.The monitoring results of settlement indicate that the increase of preloading height can significantly effect the increase of soft-foundation consolidation and settlement.the settlement rate is greater at the beginning of loading and medium-term of loading,the settlement rate reduce obviously at the later-term of loading and the time of preloading,so strictly control the size of rating loading and settlement rate are very important at the beginning of loading and medium-term of loading.Sand bag well is applied to soft foundation reinforcement of overpass renovation and expansion section in road widening project can gain good reinforcement result and economic benefits,the further application is valued.