Abstract: According to the characteristics of spatial form and overstressing of goaf, using elastic-plastic theory and considering damage characteristics of rock mass, we build mechanical model of foundation beam and obtain formula of water flowing fractured zone height, and use parallel electrical testing technology to detect development height of roof water flowing fractured zone in Pansan Mine 1622 (3) working face, the results showed that: the development height of roof water flowing fractured zone is 50 m, 12.8 times of the average mining height. Compared theoretical calculation value of 49.3 m with the measured data of Pansan Mine, it illustrates that the theoretical values are consistent with the measure data of Pansan Coal Mine, and we proved the correctness and reliability of formula.