Abstract: The friction characteristics of the column-soil interface is important to the load transfer mechanism of geo-encased stone columns. In this study, model tests are conducted using a large direct shear device to investigate the effects of the normal stress, water content of soft soil, relative density of stone materials and geosynthetic on the characteristics of the column-soil interface. On this basis, the discrete element method is adopted to study the influences of geosynthetic application, aperture ratio of geosynthetic and geosynthetic stiffness. The results indicate the interfacial shear strength increases with the increase of the normal stress, relative density of stone materials, aperture ratio of geosynthetic and geosynthetic siffness, and deceases with the increase of the water content in soft soil. The interfacial friction coefficient decreases with the increase of the normal stress and water content in soft soil, and increases with the increase of the relative density of stone materials and the aperture ratio of geosynthetics. The influences of geosynthetic stiffness are insignificant to the interfacial friction angle.