Abstract: The hydrochemical characteristics of groundwater are helpful to judge the hydraulic connection between adjacent aquifers. In this paper, Wudong Coal Mine is taken as the research object, and the hydraulic connections among bedrock groundwater, Quaternary groundwater and surface water are qualitatively analyzed by using general hydrochemical characteristics analysis, Piper three-line diagram and Gibbs diagram. Using the difference of Cl- concentration in different water bodies, the hydraulic connection degree between adjacent aquifers is calculated, and the hydraulic connection is quantitatively determined. The results showed that the pH of all groundwater samples ranged from 7.1 to 8, which were weakly alkaline water. As the depth of aquifer increases, the TDS of groundwater gradually increases, and the TDS of surface water and quaternary groundwater are lower than that of bedrock aquifer. The main hydrochemical types of bedrock groundwater, quaternary groundwater and surface water are Cl·SO4-Na, HCO3·SO4-Na·Ca, and SO4·Cl·HCO3-Na and SO4·Cl·HCO3-Na·Ca, respectively. Bedrock groundwater samples are affected by concentration, surface water and quaternary groundwater are affected by weathering and evaporation of rocks. At the same time, cation exchange occurred in groundwater and surface water in the study area. The connection degree between Quaternary groundwater and surface water is 0.361, which is medium. The connection degree between Quaternary and bedrock groundwater is 0.404, which is low. The results can provide a reference basis for the prediction of mine water inflow and the prevention and control of water inflow in the later period.