Abstract: Most sedimentary deposits of coal ash in existing ash lagoons are in saturated, extremly loose and weak condition. If an earthquake happens, these deposits will liquefy very easily, and the liquefaction will in turn endanger the ash-retention dams. Hence it is difficult to build successively sub-dams on these deposits with sufficient static and dynamic stability.In order to resolve the problem, accompanied with some sub-dam construction projects, based on the results of the laboratory and in-situ test, the earthquake response evaluation of the ash lagoon using an effective stress dynamic analysis method has been carried out. The earthquake-resistant improvement engineering measures also have been worked out in the paper .