Abstract: This paper mainly analyses the discharges and critical gate opening regulated by shutting of an emergency gate installed in a hydroelectric, station intake, and the hydraulic forces on the top, bottom and plate of the gate. Biased on observations of a hydrualic model test for the emergency gate shutting in flowing water and unsteady flow theory, a mathematical model has been established for simulating the hydraulic process of gates, draw-in conduits ad turbines. The computational results of some examples showed a satisfactory agreement with the observed ones.