Abstract: In view of the problems of complex operating conditions, frequent oscillations, and poor stability in the diversion and power generation system of a hydropower station, an optimized control method for the operation of a hydropower station diversion power generation system with tailrace excavation is proposed. This method aims to make full use of hydropower resources and enhance system stability. Based on the PI governor of hydropower stations, the firefly algorithm is applied for optimization. The firefly algorithm simulates the behavior of fireflies attracting each other and moving toward brighter groups. The weighted sum of the absolute values of the maximum and minimum speeds of the simulated system is taken as the objective function, and the proportional and integral coefficients of the governor are optimized using the firefly algorithm. By applying load increase and decrease conditions, the control performance of the governor in the hydropower station diversion power generation system with different tailrace excavation depths is compared. Experimental results show that the proposed method achieves better stability control performance compared to the unoptimized results and the governor optimized by the Stein method. The damping oscillation characteristics of the hydropower station diversion power generation system are significantly improved. Moreover, the firefly-optimized governor demonstrates robust performance under various load change conditions and significantly enhances the speed regulation quality of the unit.