When formulating ecological flow standards, water authorities often over-rely on hydrological methods and the 90% assurance rate standard, which frequently deviates from the actual ecological water demands of rivers. This issue is particularly pronounced in seasonally water-deficient small and medium rivers in northern China. Characterized by low flow volumes and significant differences between wet and dry periods, these rivers exhibit more sensitive and fragile aquatic ecosystems. The ecologically required flow based on current assessment standards often fails to meet the basic needs of these sensitive aquatic ecosystems, thereby exacerbating river ecological degradation. Taking the Qingjian River, a primary tributary of the Yellow River, as a case study, this paper integrates Hydrological Methods, the Tennant Method, and the Wetted Perimeter Method. Based on identifying key ecological requirements such as fish habitat and wetland water demand, the ecological flow for the main stem was recalculated. The results show that the recommended values determined by the comprehensive method are significantly higher than the current assessment standards and can better secure water supply during critical ecological stages. This study concludes and recommends that the determination of ecological flow for seasonally water-deficient rivers should abandon singular, rigid assessment standards and shift towards a dynamic strategy based on ecological integrity, considering the characteristics of both mainstream and tributaries, as well as operational feasibility. The findings provide both theoretical and practical foundations for optimizing the current ecological flow management system.