Based on the problem of gas overlimit in high gas mines, the overlying rock fissure zone unpressurized gas extraction is not effective. Taking the 11210 working face of Xinzheng Coal Power Co., Ltd. as the engineering background, the physical similarity simulation method is used to study the development characteristics of mining fracture zone of overlying rock in coal seam group superimposed mining, reveal the evolution characteristics of mining fracture of overlying rock in coal seam group superimposed mining, and determine the optimal horizon of gas extraction through field verification. The results show that: during the process of coal seam group superposition mining, a large stress concentration was formed outside the pressure unloading area, and within the pressure unloading protection range, the stress concentration phenomenon was not obvious, and the peak stress was smaller than the original stress of the Er1 coal seam; the coal seam group superposition mining caused the superposition unloading of the rock layers overlying the mining field, which resulted in superpositional changes of the displacement field of the overlying rock layers, and the maximum subsidence of the rock layers increased further; after the end of the coal seam group superposition mining, the rock overlying the mining area was subject to a superpositional change, and the maximum subsidence of the rock layer increased further. After the end of the stacked mining of the coal seam group, the rock layer in the middle of the overlying rock layer in the mining area was compacted, and the rock layer fissures at both ends were more developed, forming a certain range of fissure development area. Reasonable layer selection for drilling holes in the rift zone was determined through field tests, and the results of physical similarity simulation were verified through on-site monitoring of the drilling holes.