The Ordovician limestone in Hebi mining area was taken as example to study the influence of mining activities on karst groundwater quality. Based on the hydrochemical data of karst groundwater in different periods, this paper analyzed the source of main components of karst groundwater and the process of interaction between water and rock using the Piper diagram and ion combination analysis method. The reverse hydrogeochemical simulation of Ordovician karst groundwater was carried out using the PHREEQC software.The results show that the chemical types of karst water in studied area are mainly HCO3-Ca·Mg, HCO3·SO4-Ca·Mg and SO4·HCO3-Ca·Mg. The main water-rock processes are dissolution of carbonate rock, dissolution of gypsum and rock salt, and alternating adsorption of cations. The water quality of karst water in coal mining area was affected by coal mining activity, the contents of SO42-、Cl- and TDS in water are higher and the influence of mining activity on water quality increases with time.