Abstract: Taking 8-2 mining area of Xinhu Coal Mine in Anhui Province as the engineering background, this paper analyzes the geological characteristics of the coal beds and red strata structure and focuses on the research of the development location of overlying strata under the mining effect and the evolution laws of water flowing fracture zone. The study shows that: the overlying strata formed a double layer structure of the coal beds and red strata, which has unconformable contact between the thick red strata and the lower strata, and has the geological condition for the separation of the overlying strata; the separation position is preliminarily judged by the key layer theory, which is mainly controlled by the 5, 6, 14, 18 and 19 layers, and the major key layer of the Eogene red strata with larger thickness; the FLAC^3D numerical simulation test was used, and it was found that after fully mining of the working face, the maximum height of water flowing fracuture zone is 71 m, the maximum height of caving zone is 14 m, the ratio of height to thickness of fractured zone is 17.75; the mining change of overlying strata caused by the 8₂ coal seam mining in Xinhu Coal Mine shows that the maximum height of the water flow fracure zone is not up to the key aquifer, but we should pay attention to the impact tendency problem of the red strata and prevent the high key stratum from breaking under the impact, resulting in stope impact and water damage accidents.