Abstract: Strengthening anchor pieces were applied to a geogrid to form a biaxial geogrid with the anchor pieces that had three-dimensional reinforcement effect. Interaction characteristics of reinforcement and soil interface were investigated in this study using a pull-out experiment, and pull-out resistances of the reinforced geogrid in different conditions were examined by reorganizing and analyzing nine sets of test data. The results indicate that the pull-out resistance of a reinforced geogrid is greatly improved relative to the common geogrid. Strengthening effect is more obvious with larger pull-out normal stress, but it is weakened by increasing the spacing of anchor nodes. By our experimental results and theoretical analysis of anchor pieces strengthened geogrids, cohesion and friction angle between its reinforcement and soil are also increased. As pull-out normal stress increases, the interface friction gradually grows into the dominant factor in ultimate pull-out resistance.