Abstract: Aiming at the occurrence of hard and thick strata in the overlying strata, a similar model of the hard and thick strata overlying the working face was made by using the method of similar material simulation test, and the structure of the overlying strata and the evolution characteristics of fissures under the hard and thick strata and the analysis of the causation of disasters were studied. The research results show that after the advancing of the working face, the overlying rock layer gradually forms a trapezoidal structure, and the existence of the hard and thick rock layer shields the longitudinal development of the trapezoidal structure; Most of the space created by the gas accumulation creates space for gas accumulation; the fractured fractures and the abscission fractures are connected to each other, forming two-way intercommunication vertical fractured fracture areas on the working face side and the incision side, providing a path for gas migration. The gas released near the mining coal seam enters the maximum abscission crack in the overlying rock along the vertical fracture areas on both sides, and finally accumulates in the maximum separation crack under the hard and thick rock layer that occupies most of the space for coal seam mining.After the hard thick rock stratum is broken, the gas space decreases sharply, the gas pressure rises rapidly, and the gas flows to the working face through the vertical fracture fissure area on both sides, which is easy to induce gas outburst and other disasters.