Abstract: In order to study the failure degree and characteristics of coal seam roof in coal mining, the direct roof and indirect roof are simplified to a stacked beam model with horizontal and vertical joints, and the stress potential function in elasticity is introduced to analyze the size and shape of the failure region of coal seam roof combined with Mohr-Coulomb strength criterion, which is further verified by 3DEC software. The results show that the failure of coal seam roof can be divided into separation caused by horizontal joints and faults caused by vertical joints, the failure domain of separated layer is "quasi-hyperbola" distribution with steep upper and lower plane, and the fracture failure domain is arched distribution. With the increase of the elastic modulus of the indirect top, the width and height of the separation layer of the direct roof decrease obviously, and with the increase of the height of the indirect top layer, the fracture height ratio of the indirect top decreases gradually, and the width of the separation layer increases gradually. This shows that when the layer height is determined, the stress of the coal seam roof is transferred to the hard rock, resulting in a larger area of failure area; when the lithology is determined, the larger indirect top height can significantly reduce the fault height and increase the separation failure width. This study can provide relevant theoretical basis for practical engineering problems in the field of coal seam roof failure.