Abstract: Due to the differential distribution of physical properties between strata, the mechanical characteristics of bolt in composite roof have complexity, but the relevant literature is rarely reported.This paper establishes and deduces the mechanical model in the composite roof, and analyzes the mechanical characteristics of the bolt anchorage section which can effectively predict the bolt displacement on both sides of the roadway and in the roof, and provides support for improving the supporting effect of the roadway.The research methods and conclusions provide an effective new way for the mechanical characteristics analysis and support design of the bolt in the composite roof.Based on the theory of Pile Foundation Balance, through theoretical derivation, MATLAB analytical calculation of project case and FLAC^3D simulation comparative analysis, the correctness of mechanical model of bolt in composite roof is verified.The results show that the distribution forms of bolt displacement, axial force and shear stress on the cementing surface are piecewise exponential functions, and piecewise boundaries are the position of the rock boundaries, anchor bolt axial force appears infection point at these positions, shear stress breaks out at these locations; shear stress peak value mainly occurs at two locations:one is near the junction of the free section and the anchorage section (when the anchorage is in the form of end anchor), or the root of the bolt (when the anchorage is in the form of full anchor), the other is the bottom edge of rocks with relatively large shear modulus.With the increase of the shear modulus, the shear stress on the bonding surface of the bolt increases, and the response degree gradually increases from the upper boundary to the lower boundary.The internal shear stress of other layers decreases gradually, and the larger the distance, the smaller the amplitude and amplitude.