In order to ensure the safety of the hydropower station with long water transportation system while load changing,based on unsteady flow differential equations of pressure and characteristic-line method,a pipeline a numerical simulation model of the water power station with one chamber and four hydraulic turbine sets is built with SIMULINK of MATLAB platform.With the numerical model,the simulations of the hydraulic transition process of Muzhati hydropower station are conducted.The highest and the lowest surge,the rate of rise in maximum rotor speed of turbine set,the most pressure in spiral case inlet are calculated.The results show the large generator unit is a major gating factor during the hydraulic transient process in the complicated hydraulic station composed by different turbine sets.