Abstract: Aiming at the single bolt and single lap connection structure in composite laminates, a more reasonable four-stage stiffness model was proposed. Based on the traditional three-stage stiffness analysis model, this model adopted partial slip theory to improve the stiffness of the viscous stage. In addition, by taking into account the asynchronous sliding between the laminates and between the gasket and the laminate, a partial slip phase was increased. The theoretical analysis process and using conditions of the new stiffness model were given. In the ABAQUS software, a corresponding three-dimensional finite element model was established to verify the accuracy of the improved model. At the same time, the comparison between the independent modeling of the laminate and the homogeneous modeling shows that the independent modeling was more realistic. Finally, the effects of bolt hole clearance, torque, layer thickness, width-to-diameter ratio, liquid gasket and layer angle on the stiffness of composite bolt connections at various stages were analyzed. The results show that the bolt hole gap causes the screw to be bent twice, which reduces the joint stiffness. Compared with the influence of the aspect ratio, the thickness of the ply has a more significant influence on the stiffness of the bolt joint. Different ply angles have different effects on the stiffness of bolt joints.