Abstract: To study the groundwater runoff and water chemistry characteristics of the primary minable seam No.3 of coal reservoir in Shanxi Formation in the southern block of Shizhuang, southern Qinshui basin, this paper collected water samples from coalbed methane wells in the south of Shizhuang block. The characteristics of ion concentration and hydrogen-oxygen isotope are determined to analyze the distribution characteristics of ion concentration and isotope. The results show that the produced water from seam No.3 was supplied from atmospheric precipitation and was also characterized by ¹⁸O and D drift. δD and δ¹⁸O which increased from the east to the west, presented a positive correlation with ion concentration, which was consistent with the characteristics of the transition from runoff area to residence area in the study area. δD and δ¹⁸O can be used as effective exploration tool in judging the runoff conditions and evaluating exploration target.