Abstract: For the system’s joints with a typical satellite truss structure and with a 3-DOF kinematic model, with gap and hysteresis nonlinearity described by the Iwan’s model, the frequency response is studied, and the two types of responses caused by the two kinds of nonlinearity are compared. The effects of the gap size, the preload (gravity), the system damping ratio, the random gaps, and the parameters of the Iwan’s model on the nonlinear response are discussed. It is found that the gap in the joints under a preload condition can cause the “hardening-softening spring” frequency-shift phenomenon for a particular satellite structure, and the “frequency-shift” in frequency response curves obtained by the two types of nonlinearity shows different characteristics.