Abstract: In order to study the impact of goaf water on the lower coal group mining, taking goaf water situations in Dayangquan Coal Mine No. 3 coal and its geological conditions as background, the paper estimates the impact of goaf water on the lower coal group mining by calculating the height of caving zone, the water flowing fracture belt, and the damage depth of goaf water area floor, and analyzes the water flowing characteristics, then provides the basis for correctly dealing with the goaf water and ensuring safety in mine production.