Abstract: To explore different characteristics of pressure relief in the protective layer mining process of composite coal seam group, under the condition of double pressure-relief mining of closed distance coal seams group, we study the strata fracture development characteristics and stress distribution with time and space evolution. Through the similar material experiment and computer numerical simulation, the results show that the double pressure-relief mining results in complicate process of some of the overlying rock fracture, such as second expansion, compaction and match. Part of the crack develops to the deep in the space, and the fracture zone height increases in the vertical. The stress achieves redistribution under the influence of initial mining protective layer, and forms five stress area in the mining process, the effect is more significant on both ends of the mined-out area under the condition of double pressure-relief, the stress concentration factor is relatively higher to initial mining protective layer; compaction speed is faster than initial mining protective layer of mined-out area; unloading degree and range of protected layer are significantly increased.