Abstract: Taking 3^# coal seam of Santaijie Coal Mine in Yuyang as an example, this paper studied the development laws and maximum height of water flowing fractured zone with two kinds of method such as theoretical calculation and numerical simulation. The results show that the theoretical formula calculation value and the result of numerical simulation have a good consistency, they both show that the water flowing fractured zone caused by mining 3^# coal seam will not affect the main aquifer; the result of numerical simulation is more close to the calculation value with theoretical formula from the regulations of buildings, water, rail and main roadway coal pillar design and coal mining, so that maximum height of water flowing fractured zone as 60 meters is more reliable.