The goal of this study was to expand existing knowledge to genesis of high arsenic groundwater and to reveal the influence of anthropogenic practices on high arsenic aquifer system, finally to provide the comprehensive theory for developing appropriate water treatment technologies. High arsenic groundwater is distributed at depths of 10–40 m in the north of Hanjinghouqi county along the Yin Mountains where is the ecotone of the polymetallic sulfide mining area and the irrigation area. Dissolved As concentrations in groundwater are in the range of 0.5 μg L−1 to 764.8μg L−1 with an average of 161.6 μg L−1. 66.88% of (103) groundwater samples exceed the standard for allowable arsenic concentration 10 μg L−1 in drinking water. High arsenic in the ecotone is geological origin and influenced by anthropogenic activities including irrigation and mining.