Abstract: The hydro-turbine regulating system plays a key role in the safe and stable operation of hydropower plants. Improper regulation parameters can weaken the damping of the system and induce hydropower unit power angle oscillation behavior. In order to ensure the stable operation of hydropower units,this paper proposes a fuzzy sliding mode control strategy based on improved reaching law and sliding manifold. Firstly,considering the mutual influence between the transient characteristics of hydraulic and electromechanical systems,a hydro-turbine regulating system containing the internal characteristics of the hydraulic turbine with elastic water hammer and the third-order generator model is established,and the oscillation characteristics of the system under different operating conditions are analyzed. Secondly,the stability of the system rotor angle is enhanced by introducing Δδ and ΔV_t into the sliding manifold to improve the influence of the controller output on the system damping. On this basis,taking the mechanical power of the system as the reference index,a variable speed reaching law based on the exponential law adjustment is designed,so that the convergence speed can be adjusted in time with the change of working conditions.Simulation results under different working conditions show that the proposed control law can effectively improve the power-angle oscillation behavior of the hydropower unit and suppress the occurrence of low-frequency oscillation of the system when the system is subject to power disturbance,which enhances the stability of the system and the robustness of the controller.