Abstract: With the large amount of wind power, photovoltaic and other renewable energy have fed in, the power grid structure is becoming increasingly complex. In this context, hydropower units will often operate under variable conditions as required, and the operating environment will become harsh. Its traditional PID control strategy is obviously difficult to achieve optimal control under various complex conditions.Therefore, the generalized predictive control（GPC） is applied to hydropower units and its parameters are optimized based on gravity search algorithm（GSA） to realize the adaptive predictive control of hydropower units based on GSA-GPC. The simulation results show that, compared with the traditional PID controller, the designed adaptive predictive controller based on GSA-GPC has excellent regulation performance under different working conditions, and realizes the optimal control of hydropower units under multiple working conditions.