Abstract: Rockfill is unstable because of the magnification of earthquake acceleration on the top of high rockfill dams located in strong earthquake areas. To improve the strength and stability of the rockfill, reinforcement for the rockfill at the upper part of dams is an economical and effective measure. Geogrid has been widely used in aseismic reinforcement because of its superiority in interaction with rock and earth. 240 m-high Changhe Dam core rockfill dam is taken as an example, and the aseismic strengthening effect is analyzed when geogrid is used in the rockfill of dam crest. Dynamic response of the reinforced dam is analyzed by means of the time-history method. The results are introduced into the finite element method for slip surface stress analysis to investigate the effectiveness of restricting permanent deformation of high reinforced rockfill dams based on the Newmark’s sliding mass method. The results indicate that during the earthquake the force on the geogrid is much less than its tensile strength, and reinforcement has little influence on the dynamic response of the dam. But once slope slips, the reinforcement reduces the permanent deformation up to 40%~50%, limits lateral movement of the rockfill at the dam crest effectively and improves the aseismic stability of high rockfill dams. The stability is sensitive to reinforced length and vertical spacing, and their rational values are 40~60 m and 1~4 m respectively.