Slip often occurs when the bolted connection structure is loaded， and this slip will affect the dynamics performance of the structure， and then affect the performance and life of the structure. In this paper， taking the double-bolt connection structure as the object， the influence of slip on the structural modal characteristics is studied by experiments and numerical simulations. The experimental results show that the increase of the preload will lead to the increase of the resonant frequency， and with the increase of the excitation amplitude， the resonant frequency decreases and the gradient of the energy dissipation per cycle to the modal force increases. Based on the experimental results， combined with the Iwan model theory considering slip， a nonlinear dynamics model is established， and the fourth-order Runge-Kutta method is used to solve it. According to the calculation results， the structural mode under the condition of macro-slip is analyzed， and it is found that the resonance frequency drop in the second-order elastic mode increases， and the gradient of the energy dissipation to the modal force decreases. The numerical calculation model can well characterize the modal characteristics of the bolted connection structure， and the calculation efficiency is high.