Abstract: After the closure of metal mines，the underground hydrogeological conditions have changed significantly，and the residual mineralized bodies and surrounding rocks have undergone water and oxygen reactions，which in turn affect the evolution of the groundwater chemical field and form serious heavy metal pollution water environment problems. Taking a closed mine in Tongling as the research object，the back⁃ ground point，mineralized surrounding rock and mine groundwater samples are collected and tested. Based on the analysis and test data，the groundwater hydrochemical types are divided，the characteristics of heavy metal pollution are evaluated，and the main control factors of hydrochemical genesis are clarified. The re⁃ sults show that the sulfur-containing minerals are exposed to air due to mining. The ORP test shows that the oxidation of groundwater is strong，and the hydrolysis of sulfide minerals becomes an important water-rock interaction，which controls the evolution of groundwater hydrochemical type from Ca-Mg-HCO3 type to Ca�Mg-SO4 type，making the groundwater strongly acidic ( pH<2.5 )，metal ions precipitate，TDS mass concen⁃ tration increases，and heavy metal pollution such as Cu，Cd，Zn and Ni is produced.

Key words: closed metal mines, groundwater chemical characteristics, water-rock interaction