Abstract: Poyang Lake has a significant regulating and storage function on water flow, sediment, nitrogen, and phosphorus, etc from the Yangtze River and ‘Five Rivers’. However, due to the storage by upstream reservoirs, lake bed deformation and the continuous adjustment rivers and lake systems, the input concentration and loads of sediment and key nutrients and related the retention in Poyang Lake have been significantly changed, and the mechanism and process of its change and key driving stresses required identified. In order to calculate on the transport process and retention changes of water and sediment, nitrogen and phosphorus in Poyang Lake, series of data were collected, including runoff and suspended sediment concentration data at seven hydrological stations of the ‘Five Rivers’ around Poyang Lake from 1958 to 2021, topographic data at typical cross sections in the Poyang Lake inlet channel from 1965 to 2020, water quality monitoring data from 2003 to 2021, and remote sensing interpretation of lake reclamation zone from 1973 to 2018. Statistical, comparative, double cumulative curve and mass balance methods were used to analyze the trend of sediment inflow from the ‘Five Rivers’, the bed deformation of the Poyang Lake inflow channel, and the changes in TN and TP retention rate in the lake region. The results show that: The sediment inflow from ‘Five Rivers’ to the lake shows a significant decreasing trend; The outlet riverbed of Poyang Lake experienced strong vertical deepening and lateral widening at the medium beach with an elevation of 10.0~12.0 m from 2000 to 2010. The vertical deepening significantly was slowed down from 2010 to 2020, and the lateral widening under the elevation of medium beach riverbed appeared at some degree. The loads of TN and TP input and output of the lake are directly proportional to the load of sediment. From 2003 to 2021, the yearly retention rate of TN and TP in Poyang Lake decreased significantly. Analysis shows that the operation of various large and medium cascade reservoirs in the ‘Five Rivers’ Basin has significantly reduced the sediment load into the Poyang Lake area over the years and the basin’s resilience to soil loss is increasing by the enhancing soil and water conservation projects since 2000; However, sand mining and waterway regulation project in the lake area significantly deepened the riverbed of the Poyang Lake outlet; The sand mining and dredging have caused disturbance to the sediment process in the Poyang Lake-river system, partly resulting in the release of nitrogen and phosphorus in the sediment, increasing the load of TN and TP out of the lake, and to some extent reducing the retention rate of TN and TP in the Poyang Lake.