Thirty-four large-scale barrier lakes induced by the Wenchuan earthquake on May 12 occurred， in the meanwhile enormous potential risk existed, especially Tangjiashan barrier lake attracted much attention from all over the country. The barrier lake commonly can cause catastrophic damages to the downstream as well as upstream. The damages include lives and property loss by water level rising in upstream and dam-break flood in downstream. In consideration of the characteristics of barrier dam emergency treatment, the authors evaluated the seepage stability of the barrier dam, and identified the form of seepage failure and extent of induced damage. In addition, seepage analysis has been performed in the case study of Tangjiashan barrier lake in order to provide a reference for the further study on safety assessment of barrier dam.