MIKE 11 calculation software is applied to build Karot Hydropower Station dam break hydrodynamic mathematical simulation model.Dam break mathematical model is composed of river network module, section module, parameter module, structure module and boundary module.Water flow process simulated by Karot Dam Break Model is as follows: before dam break, flow is discharged by flood releasing structures, reservoir level rises; after dam break, river channel permits flow, and its model is generalized as Figure 2.2) Section Module Section module contains three parts: river channel section data, Karot Dam level-volume curve, and Mangla reservoir level-volume curve, the latter two parts are mainly used to simulate dam-retained channel storage volume.Channel section: There are 75 measured sectional data within the modelling range provided by the Hydrology Bureau of Changjiang Water Resources Commission.