Abstract: Highly wetted loess is a kind of loess with high water content,degree of saturation and compressibility.Its mechanical strength decreases apparently when water seeps in.Its mechanical property varies with the water content,which will influence the project construction.In this paper,on the basis of several kinds of in-situ testing and the construction of gravel pile composite foundation in highly wetted loess subgrade treatment in an express way project,the strength and deformation of the subgrade before and after treatment are analyzed,the mechanical properties of the highly wetted loess are further studied.Finally the applicability of various construction technology of gravel pile composite foundation treatment in highly wetted loess as well as the key points in foundation treatment are discussed.The presented results are good reference for similar engineering practice.