The paper studies the effect of elastic preloading constraints on structural dynamics of large space deployable structures with joint alearances. Based on the axial tension model, a 3D beam element of the axial tension joint was constructed. Then, considering the nonlinear mechanical behavior of the elastic pretensioned joint, the dynamic equations of the full structure were established based on KelvinVoigt contact model and Coulomb friction model. The influence of preload force on the structural vibrations was analyzed. The results showed that under the nonlinear joint constraints, the vibration transmission at high frequency increases, and the energy of low-order modes is transferred to the higherorder ones.