In order to study the mechanism of reinforcement-soil interaction, pullout tests were carried out to investigate the effect of normal stress, compaction degree and water content of backfills on interaction mechanism of reinforcement-soil interface and reinforcement displacement. The research results showed that geogrid displacements obviously lagged behind the displacement at loading end of geogrids, and with the increase of distance away from loading end, the geogrids displacements tended to decrease nonlinearly. An increase in normal stress, compaction degree or water content caused to the decrease in geogrid displacement for the condition of the identical pullout force and the location of measured points, moreover, the farther the location of measured points is, the weaker the effect of above-mentioned factors on geogrids displacements was. During the pullout tests, the main failure modes included the geogrid pulled out fully and failure of geogrid, and the peak pullout forces were approximately linear with the displacement at loading end. The peak pullout forces were closely related with the normal stress, compaction degree, water content or pullout rate. To increase compaction degree or water content of backfills, which caused to enhance interface interaction of reinforcement and soil, contributed somewhat the increase of friction angle of reinforcement-soil interface, and however made the apparent cohesion of interface increasing remarkably, and the apparent cohesion of reinforcement-soil interface reached the bigger value when the water content of backfills equals to the optimum water content.