Abstract: The river network area of the southern plains of China is criss-crossed by rivers, but the slow-moving water in cut-off channels and small rivers results in weak self-purification capacity, posing a serious challenge from agricultural surface pollution. To enhance the water purification function of ditches and beaches in the plains river network area, it is imperative to integrate their characteristics and implementc ollaborative management strategies tailored to local conditions, encompassing ditches, ecological ponds, disconnected beaches, and small rivers. This paper focuses on the typical ditches and beaches of Taihu Lake Basin, specifically addressing the issue of nitrogen and phosphorus migration. Through continuous in-situ monitoring of nitrogen and phosphorus concentration changes in different forms within ditches and ponds during the rice growing season, the study assesses the effects of three synergistic management measures for ditches and banks: fully enclosed, semi-enclosed, and fully open. The analysis delves into the spatiotemporal dynamics of nitrogen and phosphorus migration characteristics, identifies the main influencing factors, and clarifies the impact of the different ditch and bank management stratigies on nitrogen and phosphorus removal rates The results showed that, on the time scale over the rice growing season, nitrogen and phosphorus concentrations in ditch pond water decreased and stabilised after the 7d of fertiliser application, highlighting fertiliser application as the main factor influencing these concentrations, Spatially along the water flow pathway from rice field to the entrance of rive, the different ditch-bank synergistic management measures were the key factors influencing the nitrogen and phosphorus migration. Under the three different ditch-bank synergistic management measures emerge as key factors influencing nitrogen and phosphorus migration. Under the three management strategies, TN and TP concentrationsdecreased along the course of the ditch. In the fully closed mode, the average removal rates for TN and TP were 45.15% and 55.40%, respectively. Notably, the drainage water from the fully closed mode ditch pond was recycled into farmland after storage, minimizing the environmental risk of polluting surrounding water bodies.The semi-closed type demonstrates excellent purification and absorption of nitrogen and phosphorus in paddy retreat water, with average removal rates of 60.28% for TN and 74.75% for TP, significantly reducing the pollution risk to the receiving river. In contrast, the open-type model shows lower removal rates of 22.27% and 18.18%, yet still contributes to nitrogen and phosphorus removal.Overall, the synergistic management of ditches and banks for nitrogen and phosphorus interception and purification proves effective in maintaining surface water quality standards and reducing the risk of paddy field pollution to the surrounding environment.Overall, the synergistic management of ditches and banks for nitrogen and phosphorus interception and purification proves effective in maintaining surface water quality standards and reducing the risk of paddy field pollution to the surrounding environment.