Abstract: To address the limitations of traditional ground-based monitoring methods for algal blooms in reservoir tributary, such as time-consuming, labor-intensive, limited coverage, and insufficient in spatial representativeness, this study proposes a method for extracting the distribution and severity levels of algal blooms based on satellite remote sensing technology.Taking a typical algal bloom event in the Shennong Stream, a tributary of the Three Gorges Reservoir area, from July 8 to 21, 2022, as an example, we systematically analyzed the spatial distribution characteristics and dynamic evolution trends of the algal bloom outbreak by integrating field monitoring data and reservoir operation data.The effectiveness of the "tidal-like" ecological regulation implemented by the Three Gorges Reservoir in controlling algal blooms in tributaries was quantitatively evaluated.The results demonstrate that compared with Landsat-9 satellite data, Sentinel-2 satellite imagery with higher spatial resolution offers superior performance in identifying algal bloom distribution and extracting textural features.It successfully captures the entire process of the algal bloom in Shennong Stream, from outbreak and development to dissipation, as well as the significant reduction in both the distribution area and severity of the bloom following the implementation of ecological regulation.This study confirms the inhibitory effect of the "tidal-like" ecological regulation on algal bloom development, not only providing a new technical approach for researching the formation mechanisms and control strategies of algal blooms in reservoir tributary but also offering a scientific basis for ecological regulation practices in reservoirs.