Transmission tower-line systems are important electrical and energy infrastructures, which are exposed to harsh environment in the open air. The dynamic responses of transmission tower-line systems under strong external excitations are remarkable due to their flexibility. Many damaging events of transmission tower-line systems induced by strong wind, earthquakes, ice and corrosion that caused severe losses have been reported across the world. Therefore, the research and engineering applications on monitoring, safety evaluation and disaster mitigation of transmission tower-line systems have been actively conducted at home and abroad. The mechanical models of transmission tower-line systems are crucial for the monitoring, evaluation, and disaster prevention of transmission infrastructure. From the viewpoint of mechanics, a transmission line presents the properties of small strain, large deformation, and strong geometric nonlinearity. The mechanical models of transmission tower-line systems are more complicated in comparison with those of traditional high-rise towers, which can be constructed based on knowledge of finite element, stochastic vibration, wind engineering, earthquake engineering and structural analysis, etc. The mechanical models of transmission tower-line system are complicated and multidisciplinary. Many research works are still immature. In this paper, we present a state-of-the-art review on the mechanical model of transmission tower-line system and compare the advantages and disadvantages of various models to summarize the defects and to predict the future development.