In this paper, we pay attention to studying the switched model of the hydro-turbine governing system by introducing the concept of the switching of operational conditions. More specifically, utilizing the data of an existent hydropower station in China, we propose six nonlinear dynamic transfer coefficients of the hydro-turbine which can better describe the dynamic characteristics of the hydro-turbine governing system in the process of load rejection transient. Moreover, the elastic water hammer-impact of the penstock system and the nonlinearity of the generator for the process of load rejection transient are considered. Based on the combination of the different regulation modes of the governor and the corresponding running conditions of the hydroelectric generating unit, a novel nonlinear dynamic switched mathematical model of the hydro-turbine governing system is finally established. Meanwhile, the nonlinear dynamic behaviors of the governing system are exhaustively investigated using numerical simulations. These methods and analytical results will supply some theory bases for running a hydropower station.