Abstract: In view of the need of fast frequency response under high power loss,the common static model cannot depict the dynamic frequency characteristics of hydropower units with external parameters changes accurately. Based on the working nature of the fullparameter model of mixed flow hydraulic turbines,this paper establishes a dynamic model of the hydraulic turbines that considers external parameters. The model assumes that the stroke of the hydraulic turbines relay changed according to the straight-line law,and the flow coefficient and efficiency of the hydraulic turbines are equal under different working conditions. Case studies show that the dynamic model of the hydraulic turbine can not only avoid the complicated calculation of parameters of the full-parameter model,but also depict the dynamic characteristics of the fast frequency response of the hydropower units relatively accurately. The model can be applied to related calculations and simulations,where the dynamic frequency response capability of the mixed-flow hydropower units can be accurately estimated under different working conditions of the unit,which provides a basis for rational allocation of frequency response resources.