In order to explore the impact of the Nancao channel regulation phase I project on the ecological change of Jiuduansha wetland in the Yangtze Estuary，we investigate the abiotic and biological factors in the waters near the wetland in 2017，2019，2020，compare the monitoring data of hydrodynamic conditions，water quality and sediments in the wetland before and after the construction，analyze the impact of the project on the abiotic environment，use the biodiversity analysis，remote sensing interpretation and other methods to analyze the impact of project on the biological factors. The results show that the regional hydrodynamic conditions，water quality and sediment factors fluctuate before and after construction，but there is no significant change. The diversity of planktonic and benthic organisms increase，and the vegetation area expands year by year，the implementation of Nancao channel phase I project does not have a significant adverse impact on the ecological status of Jiuduansha wetland，and the project also plays a positive role in the increase of wetland diversity.