The construction and operation of cascade reservoirs in the Upper Yellow River Basin have altered the hydrological regime, adversely impacting the river's aquatic ecosystem. To develop reservoir operation strategies oriented towards ecological protection, this research first determined suitable ecological flow ranges for key mainstream control sections using the Indicators of Hydrologic Alteration - Range of Variability Approach (IHA-RVA) method. Subsequently, a multi-objective optimization model for cascade reservoir operation incorporating ecological flow requirements was established. Systematically analyzing operation scenarios across three characteristic hydrological years (wet, normal, and dry), the study quantified the trade-off relationship between hydropower generation and ecological conservation, explored the potential for synergistic benefit enhancement through coordinated reservoir operations. The findings offer a scientific basis for optimizing the operational policies of cascade reservoirs along the Yellow River mainstream.