Abstract: In order to find out the chemical characteristics and causes of groundwater in Yuanyanghu Mining Area, and to provide basis for the prevention and control of water disaster in the mining area, the aquifer hydro-chemistry of Quaternary, Cretaceous, Zhiluo Formation, 2#-6# coal seams, 6#-18# coal seams and below 18# coal seam in the mining area was analyzed. The results show that K++Na+ is the main cation, and SO42- and Cl- are the main anions, and these four ions are the main sources of TDS. Groundwater in Quaternary aquifer is mainly controlled by weathering and leaching of rocks and minerals, while groundwater samples of other aquifers are basically affected by evaporation and concertration to varying degrees. According to the chlor-alkali index of groundwater, cationic adsorption exists in different degrees in all aquifers. The chlor-alkali index decreases gradually from the deep aquifer below 18# coal seam to the shallow Quaternary aquifer, and the alternating cation adsorption is strengthened, and the contents of Ca2+ and Mg2+ decrease continuously. The groundwater of each aquifer is affected by desulphurization acid in different degrees. According to ion ratio analysis, the hydrochemical compostion of each aquifer mainly comes from the dissolution of rock salt, among which Ca2+ and Mg2+ come from the dissolution of silicate and evaporite. From isotope analysis, it can be found that Quaternary groundwater is mainly supplied by precititation, and evaporation leads to enrichment of heavy isotopes in groundwater of Zhiluo Fromation and Yan’an Fromation between 2#-6# coal seams, and there are different degrees of mutual transformation among aquifers, and they are supplied by other aquifers.