Centrifuge tilting tests were conducted to study the effects of geogrid properties on seismic stability of reinforced embankment. It was found that the stability of the embankment was influenced by shape and stiffness of the geogrid. Deformation of the reinforced area was especially limited within the confined area with the geogrids of high stiffness. Therefore, the steep embankment could be stable. Stability analyses were made by using the two-wedge method. Failure mode of the embankment and the horizontal seismic coefficient at failure were well expressed in the analysis by using the reduced pullout resistance, which was determined from results of pullout tests.