Abstract: Affected by human activities, the Poyang Lake outlet channel into the Yangtze River has undergone significant erosion over the past 20 years, which has profoundly impacted the hydrodynamic processes of the lake area receiving water from the five major rivers and flowing out of the lake area.A high-precision 2D hydrodynamic model was constructed based on measured cross-section and hydrological data.Four scenarios were designed using the model: original condition, slight erosion (-0.5 m), moderate erosion (-1 m), and severe erosion (-2 m).The influence of erosion and deposition changes in the Poyang Lake outlet channel on the hydrodynamics of the lake area was quantitatively analyzed.The results show that: ① Spatially, the northern lake area (Hukou-Duchang section) responds most significantly to erosion.Under strong erosion, the water level at Duchang Station decreases by 0.55 m in the dry season (January), and the average flow velocity in the river channel section decreases by 0.05 m/s.In contrast, the southern lake area (Tangyin-Kangshan section) shows a weak response, with an average water level decrease of 0.1 m and a velocity increase of 0.01 m/s.② Temporally, the response of Poyang Lake to erosion is strongest in the dry season (January), resulting in a marked water level decline and increased outflow from the lake area.In the wet season (July), due to large inflow and high water levels, the lake is almost unaffected, with water level differences at stations under different scenarios less than 0.01 m.③ As the degree of erosion increases, the discharge at the lake outlet increases, with a maximum increase of 190 m³/s, and the daily average discharge rises by 5.48%.④ Under strong erosion, the 30-day flood regulation capacity of Poyang Lake decreases from 6.979 billion m³ to 6.931 billion m³, and the flood storage ratio decreases from 25.99% to 25.81%.⑤ The area of Poyang Lake decreases with increasing erosion intensity.Under strong erosion, the maximum reduction in water level occurs during the rising period (March), with a decrease of 43.12 km² (-2.27%), while during the wet season (July), the reduction is only 6.37 km² (-0.21%).These findings reveal the influence of erosion and deposition of the Poyang Lake outlet channel into the Yangtze River on the lake area′s hydrodynamics, characterized by spatial differences (strong in the north, weak in the south) and seasonal heterogeneity (strong in dry seasons, weak in wet seasons).This can provide a reference for flood and drought control of Poyang Lake and the construction of hub projects.