Abstract: Considering the characteristics of an axial-flow Kaplan turbine, an approach is proposed to optimizing the control of Kaplan turbine-generator unit, which is derived from linear matrix inequalities and based on the state feedback H∞ control. Both the guide vane opening and blade opening of a hydropower generating unit can be separately regulated during disturbance according to the optimal regulation laws thus obtained to optimize the transient process of water flow. Simulation results showed that the proposed approach can obviously reduce the disturbance effect on the system and improve the robustness of the system.