Stability of dam crest rockfill under earthquake is worth researching.The effect of reinforcement of dam crest rockfill with geogrids was studied.Quasi-static method was used to simulate seismic dynamic load.Swedish circle method considering seismic load was used to analyze stability of dam slope.The mechanics of reinforcement is investigated.The results indicate that reinforcement is helpful in increasing earthquake resistance and stability of dam slope.It also shows that effect of reinforcement becomes more evident with more layers and increased tensile strength of geogrids.