In view of characteristics such as high fine particle content,apparent structure,high organic content of soft subsoil of a project in Indonesia,we conduct lab vacuum preloading tests on undisturbed soft soil sample with high water are increased,the water content,void ratio and internal friction angle are decreased,and the compression module changes less.The structural integrity and consolidation situation would affect the drainage of vacuum preloading,so further in-situ test and study shall be conducted before starting the project.