Abstract: The comparability of disaster district recover process and water self purification process is analyzed,the concept of flood disaster "self-purification process" is presented,and the three power systems,destroy power system,self-purification power system and salvation power system,are constructed. The relations of the three power systems are established by the efficiency balance theory The problem of quantitative measure of the efficiency balance is solved by adopting disaster-after sustainable development index system. An integrated flood disaster evaluation system is constructed. The system can analyze not only the situation of disaster but also the measures of disaster reduction by local government and nation. The calculate example indicates that the system has the characteristics of the structure integrity and general evaluation,and the model of the system has the characteristics of regional and timeliness. At the same time,the system has generalization ability and can be used for other type of disaster evaluation decision.