This study proposes a dynamic modeling method based on the threaded tightening joint part with the inhomogeneous distribution of pressure. Firstly, ANSYS (a software) is used to fully analyze the statics of the assembly part. The node, element information and pressure distribution at the joint surface are extracted. The nodes in the upper and lower joints are matched based on the principle of the shortest distance between nodes. The Matrix27 stiffness and damping elements are established between two matching nodes to describe the dynamic characteristics of the joint. Secondly, the stiffness coefficient and damping coefficient of Matrix27 unit are calculated based on the joint surface pressure distribution and the Yoshimura method. Finally, the finite element models of the joint part and the individual part are integrated into the finite element model of the whole machine. Compared with the theoretical modes and experimental modes on the first four stages, the shapes between the theoretical and experimental modes are similar and correspond to each other. The error between the theoretical natural frequency and the experimental one is in the range of 0.7% to 7.2%, validating this modeling method.