Zhangcun Mine No. 15 coal seam floor is under Ordovician karst water pressure, with thin water resisting floor, coalfield coal column and fault development, mining threatened by the No. 15 coal seam mining, with moderately- complex hydrogeological conditions. Based on the problem, water soluble development characteristics and hydrogeologic condition of No.15 coal seam were summarized, the influence to No. 15 coal seam was discussed, which provided technical data for  the corresponding water prevention measures.