Abstract: In response to the problems of untimely runoff forecasting, inaccurate output forecasting, large load control deviation, untimely response, and poor output stability in the application of existing power load control methods for cascade hydropower stations, this article conducts a demonstration and analysis of the power load frequency division control method for cascade hydropower stations from the perspective of considering output constraints and electricity demand. Taking the Monkey Rock cascade hydropower station on the main stream of the Dadu River in Kangding City, Ganzi Prefecture, Sichuan Province as an example, based on the hydraulic regulation performance, the location of the cascade group, and tasks undertaken by the cascade hydropower station, the total energy storage value of the cascade hydropower station is calculated and output constraints are set based on this. Wavelet transform technology is used to predict the total load of the cascade hydropower station, and then the power load is divided into three regions: low frequency, medium frequency and high frequency region. Finally, based on the ordered power consumption plan and actual power demand of different regions, appropriate frequency division control methods and execution measures are formulated for the three regions to effectively regulate and control the power load of cascade hydropower stations. The experimental results show that the power load frequency division control method considering output constraints and electricity demand has achieved effective regulation and frequency division control of the power load of cascade hydropower stations. The proposed method has the advantages of high efficiency, small deviation, low risk, and energy conservation and consumption reduction. It has improved the efficiency of runoff forecasting for hydropower stations, reduced the fluctuation value of hydropower station output, reduced the energy loss of hydropower units, and shortened the response time of power load control It provides a solid guarantee for the stable and efficient operation of cascade hydropower stations, and has high application and promotion value.