The circumferential rod?fastening rotor structure is very common in gas turbines，and the tie rods and contact layers commonly present in the rotor structure have a very important impact on the dynamic characteristics of the rotor?bearing?seal system. In this study，a mechanical model of the circumferentially distributed tie rods and a nonlinear contact stiffness matrix that characterizes the contact effect between the wheels are established firstly. The contact stiffness matrix is composed of seven stiffness coefficients ，which can comprehensively characterize the lateral stiffness，shear stiffness，bending stiffness，and torsional stiffness of the contact layer，and the influence of rotor deformation on stiffness coefficients the matrix is considered in the matrix. Then，a dynamic model of the circumferential rod?fastening rotor?bearing?seal system is established by introducing the nonlinear oil film force model based on the short bearing theory and verified by experiments and the Muszynska sealing force model. The Newmark?β method is used to solve the dynamic equations，and the three?dimensional spectrogram is used to analyze the influence of the magnitude and uneven distribution of the pre?tightening force on the nonlinear dynamic characteristics of the circumferential rod?fastening rotor?bearing?seal system. The results show that the contact stiffness and the relative phase of failed tie rods have significant effects on the stability of the rod?fastening rotor?bearing?seal system.