Abstract: According to the double-layer mined-out area found in the north mining area of Qidashan, in order to analyze the influence law of its stability on the spatial structure of the mined-out area, blasting numerical simulation tests of different lower goaf spans are carried out directly above the double-layer mined-out area.In the process of increasing the span of the lower goaf is increased from 20 m to 30 m, the peak vibration velocity and effective stress of the nodes in the middle and both ends of the roof in the lower goaf are analyzed, and it is found that the most easily damaged goaf is in the middle and both sides of the lower goaf roof are analyzed.It is found that the middle of the lower goaf roof is greatly disturbed by blasting load.The shear safety factors and tensile safety factors of the lower goaf roof are calculated.It is found that the stability of the roof decreases with the increase of the span of the lower goaf.