Abstract: In order to study the evolution laws of water flowing fractured zone height at 8101 working face in Taian Coal Mine, we use UDEC to build mechanical model to simulate the development process of overburden water flowing fracture during the mining process from face to open-off cut, and use one terminal plugging method to measure the height of water flowing fractured zone. The results show that the height of water flowing fractured zone has a certain range with the advancing of caving face, and will stop upward development when reach to full extraction. Meanwhile, there is always stress increased area in the front of caving face and rear of open-off cut, the distance of maximum stress from the coal wall is 4 to 10 m. There is low ground stress region around the caving face and open-off cut and rich secondary interstice, which is the highest region of water flowing fractured zone, the more interstice developed. Furthermore, the result of the height of water flowing fractured measured by using the method of one terminal plugging basically consistent with the results of numerical simulation, so it is a effective and feasible method.