Abstract: Rational determination of ecological flow is fundamental for maintaining the health of river ecosystems. This study proposes a fusion calculation method incorporating weighted integration and lower-bound constraint adjustment by combining the existing Tennant method, minimum monthly flow of the driest month in the recent 10 years method, 90% guarantee rate monthly flow method, and annual distribution method. The method performance is evaluated at five control sections along the Taohe River, the largest tributary in the upper Yellow River Basin. Results show that the monthly ecological flows calculated by the fusion method exhibit clear and reasonable seasonal characteristics, effectively reflecting the ecological water demand processes required to sustain river ecological functions in different seasons. Findings can provide scientific support for ecological flow regulation and reservoir ecological dispatching in river basins.