Abstract: Before establishing an eco-electricity price mechanism, the hydroelectric power station authorities need to grasp the influences of ecological flow discharge on power generation of hydropower stations. In order to study the influences of ecological flow discharge on power generation of non-regulated diversion hydropower station, the Gini coefficient was introduced to characterize the annual uniformity of the daily average flow. The power generation and power loss of the Jiugong I Hydropower Station in Jiujiang City at different designed guarantee rates of installed capacity from 1963 to 2019 were analyzed. The results show that: ① when the Gini coefficient is similar, the percentage of power loss in wet year is generally smaller than that in dry year. When the average annual flow is similar, the smaller the Gini coefficient, the smaller the percentage of power loss. ② In the range 0~30% of the design guarantee rates of installed capacity, the percentage of annual average power loss increases as the design guarantee rate of installed capacity increases. In the range of 30%~100% of the design guarantee rates of installed capacity, the percentage of annual average power loss decreases as the design guarantee rate of installed capacity increases. When the design guarantee rates of installed capacity is 30%, the percentage of annual average power loss is the largest, with a value of 13.3%, which means this type of hydropower station has the largest loss percentage of power loss due to ecological flow discharge. The research results can provide a reference for reservoirs to improve the utilization efficiency of water energy resources under the premise of satisfying ecological water use.