Abstract: The interface characteristics of geogrids would directly influence the safety and stability of reinforced soil retaining wall.So the interface index of geogrids in different materials was important when the reinforced soil retaining wall was designed.The main influential factors in the interface characteristics of geogrids,such as test method,load mode,effect of boundary and size of test,thickness and degree of compacting of the soil,and clip of the reinforcement,were analyzed in this paper.The direct shear and pullout tests were done for geogrids in clay and coarse gravel in laboratory.Some conclusions were found from the tests that the shear strength of the interface between geogrids and the coarse gravel was high,yet the shear strength of the interface between geogrids and the clay was low.The geogrids with large stiffness and the coarse gravel backfill materials should be selected to be used for high reinforced soil retaining wall.And the shear strength of the interface between geogrids and the clay should not be determined with the direct shear friction test.