Reservoir dams have made important contributions to the development of socio -economic development. At the same time, the dam is over -frequency flood, strong earthquake, and other damage. It may induce dams to collapse and there is a risk of collapse. The Lingjintan Damage analysis uses HEC-RAS to establish a hydropower mathematical computing model from the Lingjintan Hydropower Station to the Taoyuan Power Station Dam site. The decision method was performed and analyzed the damping flood. Calculating the results of the damping flood can be proposed targeted with disaster prevention and mitigation measures. It can more effective guidance power stations and downstream cities before the flood to ensure that the rescue scheduling is based on it.