Abstract: Based on the practical needs for developing the structural health monitoring technologies of transmission tower bolted structures, a finite element model of transmission tower bolt is established based on the nonlinear acoustoelastic effect, and a multi-physics coupling numerical iterative algorithm is proposed. Firstly, based on the geometric configuration characteristics of the transmission tower bolts, a two-dimensional axis-symmetric finite element model is established. and then the Murnaghan hyperelastic material that considers the third-order acoustoelastic effect is used to realize the coupling solution analysis of the stress-strain field and the acoustic field of the bolt. Finally, the proposed numerical model and the iteration method is validated through experiment. The results show that the preload and the clamping length have a significant effect on the stress field distribution within the bolt structure, and the wave velocity variation and bolt deformation caused by the bolt preload have a dual impact on the time of flight of the ultrasonic longitudinal wave. The model and numerical method proposed in this paper can provide a numerical simulation platform for bolt preload measurement based on the nonlinear acoustoelastic effect, and can also provide a technical guidance for related experimental research and instrument development.