Through the implemention of equivalent linear elastic model into Abaqus, the paper analyzed the dynamic response of a rock-fill dam in detail by 3D FEM and researched the response rules of the maximum acceleration,the maximum dynamic shear strain, as well as the maximum relative dynamic displacement under the role of earthquake of seven degree. At the same time, it calculated and compared the seismic dynamic response of the dam in two different conditions such as input of X,Y horizontal seismic waves ,and input of seismic waves of X, Y, Z directions respectively. It also studied the impact of vertical seismic acceleration on dam under rule of earthquake of seven degree. Result shows that the vertical seismic wave barely has influence on dynamic response in horizontal directions, but has huge influence in vertical direction.