Abstract: The shear connector is the key component of a fabricated steel-concrete composite beam. Its load slip curve is roughly divided into four stages, namely, friction stage before slip, slip stage, elastic stage after slip and plastic stage after slip. In this study, through the elastic foundation beam theory and the plane stress theory of material mechanics, the stress model of a high-strength bolt shear connector is established, the stress behavior of the first three stages is theoretically analyzed, and the theoretical results are verified by several groups of experimental data, and the results are in a good agreement. The research shows that: in the stress process of the shear connector, the shear surface of the screw is subjected to the coupling action of the bending moment, of the shearing force and, of the axial force. The mechanical model proposed can accurately simulate the limit value of the bolt in the elastic stage, and can preliminarily explain the reason why the shear performance of the bolt changes with the pretension in the elastic section. It is concluded that the bending moment of the elastic section of the bolt has little effect on its yield limit.