Abstract: Three-dimensional nonlinear dynamic elasto-plastic analysis method is employed to study the seismic response characteristics of a high earth-rockfill dam in a narrow valley. The distribution rules of shear strain and permanent displacement are given with different topographies of valley. The results show that the dynamic response of the dam exhibits strong spatial three-dimensional effect of valley topography and that the shear strain and displacement of the dam has significant effects. For the symmetrical valley, the distribution of shear strain is extending out in an oval shape, and the maximum value appears at the crest of the core wall. When the shape factor of the ratio (L/H) is smaller, the constraint to the dam is stronger, and the displacement increases more obviously. Under the same ratio, the settlement of dam crest under a wider valley is larger than that under a gentler slope. The results are valuable for the design of high earth-rockfill dams with a narrow valley in meizoseismal areas.