In order to make sure the height of overlying rock fracture zone, 2D Block discrete element numerical simulation software was used to analyze the crack zone height after mining. The simulation result showed the crack distribution and inter laminar fracture distribution law, the distribution of the overburden rock fracture morphology was settled, crack partitions were sized according to the internal horizontal strata deformation value, respectively severe rupture zone, tiny fracture zone and closed area again. The fracture development rule under the mining condition was obtained. The height of the fracture zone was 246.5 m, 25 times of the mining thickness.