Abstract: To investigate whether coal mining at a certain mine in Ordos affects the overlying unconsolidated Quaternary aquifer, water samples from different sources were collected for hydrochemical testing and hydrogen and oxygen isotope analysis. A field tracer test was conducted using potassium iodide as a tracer, and the rainfall data were analyzed together with the dynamic water level changes of various aquifers. The potential impacts of mine water inflow on different overlying aquifers were comprehensively evaluated. The results show that the hydrochemical characteristics and isotopic compositions of surface water and Quaternary pore water are similar; those of Jurassic bedrock water and mine water are also similar; whereas significant differences exist between mine water and Quaternary pore water. During the tracer test, the electrical conductivity of mine water samples ranged from 350 to 375 µS/cm, and the iodide ion concentration ranged from 85 to 90 µg/L. Both parameters exhibited minor fluctuations without obvious peaks, indicating that the tracer did not reach the underground sampling point and that no significant hydraulic fracture connectivity was established between the underground discharge point and the overlying unconsolidated Quaternary pore aquifer. Correlation analysis between rainfall and water level dynamics in the four boreholes shows that, due to the barrier of multiple aquicludes, neither the unconsolidated Quaternary pore aquifer nor the Jurassic aquifer within the final depths of these four boreholes was significantly affected by coal mining dewatering. The findings can provide a basis for mine water inflow control and regional water resource protection.