Abstract:The expansive softrock in Yanji region has not been recorded in the published papers. Recently,several landslides occurred there during building of high grade road. The unexpected failure of slopes aroused close attention in the local geoengineering field. A series of tests,including creep test,direct shear test,triaxial compression test,expansion test,disintegration test and XRD technique,show that expansive softrocks exist in Yanji region and belong to high expansive softrocks by the national standard. The clay there is composed mainly by montmorillonite and mixed-layer mineral I/S with middle mixed-layer ratio. Based on research on mechanisms of failure of the slopes,the improving methods are put forward. The research on the expansive softrocks is of great significance for the treatment of slope of expansive softrocks in Yanji region.