In this paper, the historical data,field survey, statistical analysis, numerical simulation were adapted, and Canjiang River Delta wasselected as typical researeh area to aim at the efects of a water stucture on the groundwater in the Poyang Lake Basin.The boundary conditionswere determined based on regional geological and hydrogeologicaldata, dynamic relationship befween groundwater and river,regional digital ele-vation model, and historical formation and evolution of the Poyang Lake. A three-dimensional groundwater flow model for the study area was er-tablished using CMS software. Then, the flow model was used to simulate the structure impact on the groundwater aceording to the schedulingscheme of thestructure. The results show that there are big impact in dry years,large effect on the places near the river and dam, and vice versa.Thegroundwater level raised -2m, groundwater runoff altermately decreased, and soilgleization area increased by9.3% in wet year.