Abstract: In order to understand the hydrochemical characteristics and irrigation suitability of deep mine well water in Dongguashan Copper Mine，the mine deep well water (below the middle section of -790 m) is taken as the research object，and the pH value，conventional ion composition and TDS of mine well wa‐ ter are tested.The hydrochemical characteristics of mine well water are analyzed by means of Piper three�line diagram，Gibbs diagram and ion ratio method，and the suitability of mine well water irrigation is eval‐ uated.The results show that the hydrochemical types of deep mine well water in the study area are mainly HCO3-Ca type and HCO3 ·SO4-Ca type，which are characterized by lixiviation water in sedimentary rock areas.The hydrochemical indexes of deep mine well water in the study area are mainly controlled by rock weathering and hydrolysis，which are dominated by the dissolution of carbonate rocks，among which cal‐ cite dissolution is the main.According to the deep hydrogeological conditions of the mining area，it is in‐ ferred that the water filling source of deep mine well water is mainly Qixia Formation（P1q）and Huan‐ glong-Chuanshan Formation（C2+3 ）aquifer.The cation SAR values of mine well water are all less than 10， most of the SC values are less than 20，and a few are between 20 and 40. The deep mine well water in the study area is more suitable for agricultural irrigation.

Key words: mine well water, hydrochemistry, suitability evaluation