[Objective] Located in the core of the Yangtze River Delta, the Taihu Basin is a typical plain tidal river network region characterized by numerous lakes. As a key watercourse in this basin, the Huangpu River serves as a representative case for studying ecological flow, which is critical for maintaining the stability and health of river-lake ecosystems. [Methods] Utilizing flow monitoring data from the Songpu Bridge section and hydrological records (including typhoons and rainfall) from 2007 to 2023, this study analyzed instances where the daily average flow fell below the sensitive ecological flow threshold of 90 m³/s. The ecological flow compliance rate was calculated as the ratio of days meeting the assessment indicator (≥90 m³/s) to the total days in the evaluation year. To accurately determine compliance, the analysis comprehensively accounted for force majeure events and major natural disasters (e.g., droughts, floods, typhoons, and earthquakes). Furthermore, factor analysis was employed to conduct a comprehensive assessment of the factors contributing to flow deficits relative to the sensitive ecological threshold. [Results] (1) Daily average flows at the Songpu Bridge section dropping below the sensitive ecological threshold occurred most frequently between August and October (Gregorian calendar), peaking in September. These occurrences were also more prevalent prior to the semi-monthly high tides (specifically the 3rd and 18th days of the lunar month). (2) Factor analysis indicated that the primary causes for flows falling below the sensitive threshold were force majeure factors, specifically the backwater effect of astronomical tides and storm surge-induced water level rises caused by typhoons and cold air. (3) During periods of sub-threshold flow, chloride ion concentrations at the section remained significantly lower than 250 mg/L, satisfying the ecological protection targets for tide prevention and saltwater intrusion control. Consequently, after accounting for force majeure and water quality compliance, the ecological flow assessment compliance rate for the Huangpu River from 2007 to 2023 was 100%. [Conclusions] Adopting a basin-scale perspective, this study establishes a comprehensive methodology and mitigation strategies for evaluating ecological flow maintenance in tidal river systems. Given its critical geographical position, the Huangpu River is identified as a representative tidal watercourse within the Taihu Basin. This research elucidates the influence of tidal processes on riverine ecosystems, offering a reference framework for similar estuarine reaches. We recommend integrating digital twin watershed construction to facilitate a closed-loop management system characterized by “technological intelligence, refined dispatching, and diversified objectives”, providing a reference for establishing ecological flow guarantee systems in water-abundant regions.