[Objectives] The Taihu Basin is located in the core area of the Yangtze River Delta, characterized by numerous lakes and a typical plain tidal river network region. The Huangpu River is one of the key rivers in the Taihu Basin. The study of the ecological flow in the Huangpu River holds a strong representativeness and is of great significance for maintaining the stability and health of the river and lake ecosystem. [Methods] By collecting the flow monitoring data of the Songpu Bridge section and hydrological data such as typhoons and rainfall in the Taihu Basin from 2007 to 2023, we analyze the instances where the daily average flow at the Songpu Bridge cross-section fell below the sensitive ecological flow threshold of 90 m³/s over the years, and evaluates the compliance rate of the ecological flow target of the Huangpu River. The compliance rate is calculated as the number of days meeting the assessment indicator (90 ) divided by the total number of days in the evaluation year. It is necessary to comprehensively consider factors such as major natural disasters (such as droughts, floods, typhoons, earthquakes, et al.) or force majeure, so as to reasonably determine the number of days when the sensitive ecological flow is met and the number of days when it is lower than the target flow. We conducted a comprehensive assessment using SPSS data analysis method on factors below the sensitive ecological flow and the impact factors of sensitive events. [Results] (1) The results indicate that the periods when the daily average flow at the Songpu Bridge section of the Huangpu River drops below the sensitive ecological flow occur most frequently between August and October in the Gregorian calendar (corresponding to the 7th to 9th lunar months), with the highest incidence in September. Such occurrences are also more prevalent prior to the high tide days of each month (specifically the 3th and 18th days of lunar month). (2) A comprehensive evaluation and analysis of the influencing factors associated with events where flow falls below the sensitive ecological flow, conducted using SPSS data analysis methods, indicates that the primary causes are force majeure factors such as the backwater effect of astronomical tides and storm surge-induced water level rises (resulting from typhoons and cold air). (3) During the periods when the daily average flow at the Songpu Bridge section is below the sensitive ecological flow, the chloride ion concentration at this section remains significantly lower than 250, which meets the ecological protection target of tide prevention and saltwater intrusion control in the Huangpu River. Considering factors including force majeure and the compliance of chloride ion concentrations, the compliance rate of the ecological flow assessment index for the Huangpu River from 2007 to 2023 is 100 satisfied. [Conclusions] Starting from the basin scale and overall perspective, this study innovatively establishes a comprehensive methodology and mitigation strategies for evaluating ecological flow maintenance in tidal river systems..As a tidal river at the confluence of its basin, the Huangpu River is regarded as one of the key watercourses in the Taihu Basin, given its critical geographical position and typicality as a tidal water body. Research on the safeguard of its ecological flow contributes to elucidating the influence of tidal processes on riverine ecosystems, thereby offering a reference framework for studies on other analogous estuarine reaches. We recommend integrating the construction of a digital twin watershed to promote the realization of the whole chain closed-loop management of 'technological intelligence, refined dispatching and diversified objectives, which can serve as a reference for the establishment of ecological flow guarantee system in water-abundant regions.