To effectively safeguard the ecological flow of rivers and lakes, a dynamic calculation method tailored to the target guarantee rate has been developed. In alignment with current ecological flow management requirements, the target ecological flow for each month at key tributary control sections in the middle and lower reaches of the Hanjiang River has been analyzed and determined. Research indicates that the fundamental ecological flow rates of various sections within the study area, calculated using traditional hydrological methods, range from 0.492 to 7.71 m3/s, comprising 2.56% to 14.1% of the average annual flow. Due to significant variations in water inflow in the basin, the calculation results obtained through various methods differ greatly, posing challenges in ecological environment. By considering the dynamic calculation method of ecological flow that ensures the target guarantee rate, the monthly target values of ecological flow in each section have been determined to range from 1.04 to 25.2 m3/s, exhibiting an overall pattern of "higher during the wet season and lower during the dry season," which aligns with the inflow characteristics of the watershed. The analysis of daily average satisfaction indicates that the method produces highly satisfactory results. Under the condition of fulfilling the current management requirements, it can enhance the annual ecological water volume of the river by 16 to 317 million cubic meters, thereby better safeguarding the ecological water needs within the riverbed. The findings of this study can serve as a valuable reference for water resource protection, scheduling, and supervision in the Hanjiang River Basin.