Abstract: To restore the discharge capacity of the lower Dongjing River, relevant authorities organized and implemented the first phase of the river regulation project. Based on measured hydrological data from flood seasons before and after project implementation, the water level drop under the same flow rate was analyzed, a two-dimensional hydrodynamic model was recalibrated, and design conditions were re-evaluated. By comparing changes in erosion and deposition in the river section, the regulation effectiveness and its sustainability were systematically assessed using a two-factor sustainability evaluation framework of "water-sediment variation-sediment transport capacity response". Results show that after project implementation, the water level at Yanglinwei Station under the regulation flow (3 000 m³/s) was 0.06 m lower than the designed value, achieving the intended objective. Under the condition that the 2023 flood peak discharge increased by 16% compared with 2021, the water level at Yanglinwei Station dropped by 0.18 m. With water levels along the river significantly reduced under equivalent discharge, the channel flood conveyance capacity was notably improved. Actual siltation in the dredged area was limited, demonstrating the sound sustainability of the regulation project. The dredging floodplain scheme showed clear advantages in cultivated land protection and investment efficiency. The findings can provide a technical reference for the subsequent harnessing projects of the lower Dongjing River and for regulation projects in other tributaries of the Yangtze River Basin.