Abstract: In order to study the groundwater runoff and water chemistry characteristics of the No. 3 Shanxi Formation coal reservoir in Shizhuangnan Block, Southe rn Qinshui Basin, the authors collected water samples from coalbed methane wells. The characteristics of ion concentration were determined to analyze the distribution characteristics of ion concentration. The results showed that the water types of the water samples in study area were mainly Na*-HCO3-CI and Na*-HCO3- type; the st udy area had the characteristics of the transition from the runoff area ( oxidation environment) to the residence area ( reduction environment) from east to west. The co ncentration of KDS, Na+, K+, CI, Ca2+, Mg2+ and HCO3~ which increased gradually from east to west were controlled by mineral dissolution reaction, while under the d e sulfate effect, the concentration of sO42- was gradually decreased. High production wells were mainly distributed in high salinity and high ion concentration region. K DS and ion concentration indicated the characteristics of groundwater flow in the study area and can be used as reference factors for judging the runoff conditions of co al seam water and evaluating exploration target.