Abstract: Through the analysis of the roof fracture between the lower layers with different spacing of the close distance thin coal seam group, the roof structure of coal seam group can be divided into three categories: loose structure roof, block structure roof and plate structure roof according to the roof thickness. The numerical simulation model of 3DEC under different roof structures was established, and the displacement and stress distribution of roof under different propulsion distances were analyzed.The simulation results show that when the roof of the loose structure is broken, the loose structure is broken and has no bearing capacity; when the roof of block structure is broken, the block structure is broken and has a certain bearing capacity, the mining pressure is not obvious; when the roof of plate structure is broken, the plate structure is broken and has strong bearing capacity, and has the characteristics of first weighting and periodic weighting. The pressure of 3318 working face of Guandi Coal Mine was measured on site, the pace of first broken weighting interval of directly roof in 3318 working face is about 22.3 m, the pace of average period is about 19.8 m. The measured results agree with the numerical simulation results, it indicates that the roof of 3318 working face is plate structure roof.