The relationships between dynamics response and preload of bolted joint were studied. By using finite element analysis method, nonlinear model of flange structure with bolted joint was established. The transient analysis for different preload condition of bolted joint was employed to obtain steady state response. The energy of the difference signals between up and down mating surfaces was computed. The energy of the difference signals increased as preload of bolted joint decreased, and nonlinearity of bolted joint increased. The numerical results were compared with experimental measurements. The similarity was found to be satisfactory.