Based on the assumption that geogrid and its surrounding soils being a composite material,the effect of reinforcement of dam crest rockfill with geogrids is studied by using nonlinear elastic finite element method.The influence of layer number and modulus of geogrids on effect of reinforcement is investigated.The results indicate that reinforcement is helpful in increasing stability and earthquake-resistant ability of dam crest rockfill.It also shows that effect of reinforcement becomes more evident with more layers and increasing modulus of geogrid.