The mining of super thick coal seam causes more intense overlying rock activities. It is of great significance to accurately grasp the mining fracture variation law of super thick coal seam overlying rock for safe and efficient production of working face and protection of surface ecological environment. Taking the 2303 working face of a mine in Xinjiang as the engineering background, this paper intuitively describes the fracture characterization of overburden rock under the influence of mining movement of extremely thick coal seam based on discrete element numerical simulation, and reveals the development law of fracture zone and caving zone along with continuous mining of coal seam. The research results show that: The development height of caving zone and water-conducting fracture zone is 51.10 m and 148.11 m, respectively. The caving ratio is 5.77 and the fissure ratio is 16.63. With the advance of mining, the development of fracture zone and caving zone goes through three stages and two cycles: the height of fracture zone goes through a stage of development-growth-stability; The height of the caving zone experienced two cycles of sudden increase and slow decrease with the breaking of the old top and the subkey layer. Based on the discrete element numerical simulation results, fractal geometry theory is introduced and box covering method is adopted to accurately and quantitatively describe the development degree of mining overlays in extremely thick coal seams. The results show that: Under the influence of mining, the fracture development of overlying rock has excellent fractal characteristics. With the progressive advance of coal seam, the overall fractal dimension presents a dynamic change, and the overall fractal dimension presents a "saddle-shaped" feature with large at both ends and small in the middle. The average fractal dimension on both sides of the goaf reaches 1.001 and 0.978 respectively, which are the main water channels of the goaf. The development zone of the separate layer at the height of 150 m from the floor reaches 0.904, which is easy to accumulate groundwater. Based on the fractal dimension calculation results, the fractal dimension evolution curve is fitted, and the fractal evolution law of overlying rock cracks under different advancing steps is further revealed. It is inferred that the shape dimension reaches the maximum when the advancing distance reaches 71.18m, corresponding to the large-area roof caving stage. The research conclusions of this paper can provide reference and basis for the analysis of mining-induced fissure variation of overlying rock in super thick coal seam under similar conditions.