Abstract: At present,the selection of geogrid in reinforced tailings structure does not consider the influence of mesh size,but only consider the ultimate tensile strength of geogrid,which makes the geogrid selection more subjective in practical engineering. To study the influence law of mesh size on geogrid reinforced tailings,i. e. the area ratio between geogrid-tailings interface and shear surface,on the interface strength parameters of geogrid-tailings,five geogrids of the same specification with different mesh size(12. 7 mm×12. 7 mm,25. 4 mm×25. 4 mm,38. 1 mm×38. 1 mm,50. 8 mm ×50. 8 mm and 63. 5 mm×63. 5 mm) were selected to analyze the interface characteristics of geogrid-tailings through direct shear test and pull-out test respectively to explore the reasonable size of geogrid reinforced tailings. The test re- sults show that under the two test conditions,with the increase of mesh size of geogrids,for the geogrid-tailings inter- face strength index parameters,the pseudo-cohesion decreases and the pseudo friction angle increases. The change of mesh size of geogrid has a significant effect on the pseudo-cohesion,but has little effect on the pseudo friction angle. With the increase of mesh size of geogrids,the interface pseudo-friction coefficient decreases gradually and the decrea- sing range becomes slow. The larger the normal stress is,the smaller the variation range of pseudo-friction coefficient is. Under the same condition,the pseudo-cohesion of pull-out interface is about 0. 7 times of that of direct shear inter- face,and the pseudo friction angle of pull-out interface is about 0. 45 times of that of direct shear interface. In order to analyze the effect of geogrid reinforced tailings more accurately,the interface frictional effect of geogrid-tailings should be separated from the interface comprehensive frictional effect,and obtain the interface friction coefficient ratio of geo- grid-tailings. With the decrease of the area ratio between geogrid-tailings interface and shear surface,the interface fric- tion coefficient ratio of geogrid-tailings increases slightly at first,then decreases sharply,and the reinforcement effect of geogrids disappears rapidly. The reasonable mesh size of geogrids reinforced tailings should be controlled about 0. 4 of the area ratio between geogrid-tailings interface and shear surface,i. e. when the mesh size of geogrid used in this pa- per is 38. 1 mm×38. 1 mm,the effect of geogrid reinforcement tailings is the best.