Abstract: Based on historical water quality data and sampling test results, using Piper three-line diagram, correlation analysis, hydrogen and oxygen isotope, Gibbs diagram, ion ratio and saturation index, etc., the hydrochemical characteristics and genetic mechanism of the groundwater with high TDS in Xinjulong Coal Mine area were explored. The results show that with the proceeding of mine construction and coal mining, the water chemistry environment in the study area has changed. The water chemistry type is no longer a single SO₄-Na type, with SO₄·HCO₃-Na and SO₄-Ca·Mg type appearing in the deep limestone water. The high-TDS groundwater in the study area is mainly caused by poor hydrodynamic conditions in the upper layers, strong high-temperature water-rock action, obvious leaching, evaporation and concentration, and a certain degree of reverse cation substitution and exchange. The dolomite and calcite in the groundwater are in a precipitated state, and gypsum and salt rock are in a dissolved state, which are the main sources of Na⁺ and SO₄^2- in groundwater. The above conclusions not only provide a basis for studying the composition of mine water, revealing the evolution process and formation mechanism of groundwater pollution and multi-field coupling in coal mining areas, but also lay the foundation for coal mining water hazard prevention and mine water treatment and utilization in coal mining.