Abstract: The dam-break flood mathematical model, which is developed on the basis of the previous research of dam-break floods, can simulate the propagation of a dam-break flood from the reservoir tail to the dam site, the advancing of a dam-break flood in the downstream channel, and the submergence of a dam-break flood in the downstream town using a hydrodynamics method. By use of the developed dam-break flood model, prediction results of a dam-break flood with several planned working conditions show that the dam-break duration, the upstream flow of the reservoir and the water levels before the dam during the dam-break are the main influencing factors of the calculation results of the model.