Abstract: Landslide dams are formed by the blockage of river channel with soil and rock debris from rockfall,landslide and debris flow. Differ from the man-made dam,the materials of landslide dams have the characteristics of loose structure and uneven distribution. Hence,the landslide dams are prone to failure by overtopping,seepage damage and dam slope instability after their formation,which threatens the life and property safety of downstream people. Once the landslide dams are formed,their stability and failure mode are influence by the water in upstream and the aftershock. In this article,the Tangjiashan landslide dam induced by the Wenchuan earthquake is considered. The ABAQUS is used to establish the seepage and dynamic response analysis model. The stability of landslide dam under the action of seepage and aftershocks are analyzed. The influence of seepage and aftershock on the failure mode of landslide dam are discussed. The research results show that(1)the possibility of seepage failure of the Tangjiashan landslide dam is relatively small. But as the upstream water level rises,the probability of seepage failure of the landslide dam increases; (2)The dynamic response characteristics of the landslide dam shows that from top to bottom along the height of the dam,the acceleration magnification of the dam body gradually decreases,and the dynamic response presents an obvious"surface amplification" effect; (3)The Tangjiashan landslide dam would not fail under the action of aftershocks. The aftershocks can reduce the height of the landslide dam significantly,thereby accelerating the occurrence of overflow damage.