In order to reveal breakage mechanism of key strata in goaf of roadway mining zone, considering rock structure and mining effect, continuous deep beam model under uniformly distributed load is established and determination theory and method of feasibility on the upward mining is proposed. The key strata mechanical properties of 8号 coal seam is analyzed with theoretical calculation and numerical simulation analysis in Hulonggou coal mine.And FLAC3D numerical simulation analysis between the layers of rock stress field and displacement field distribution characteristics. The results show that a local scope of "internal stress arch" appear between adjacent coal pillars in the key strata after mining lower coal. If a wider range of "external stress arch" appear in the whole range of stope, there is stabilized key strata in the roof of roadway mining and the key strata effectively avoid damage of rock stratum from stress concentration, restrain the expansion of the overburden failure height. If a wider range of "displacement arch" appear in the whole range of stope, the rock stratum is destroyed and upward mining is impracticable.so the stabilized key strata plays a determinative effect for upward mining.