To reveal the factors influencing wind-induced vibration of transmission lines under complex mountain wind fields， a refined finite element model of “two towers and three lines” is established based on the actual line parameters of the 110 kV Lian’nan transmission line in Ningxia. The gravity self-balancing method was used for the shape-finding calculation of the transmission line. The harmonic superposition method is used to simulate the stochastic wind field where the line is located， and wind loads are applied to the tower-line system model to analyze the influencing factors of wind-induced vibration of mountain transmission lines. Results show that the acceleration effect of mountain wind fields is significant， with acceleration ratios reaching 1.3 to 1.4 when the wind incidence angle is 45° and the wind direction angle is 90°， which can easily induce severe line wind-induced vibrations. Compared to models without towers， the tower-line system model shows larger and more realistic wind vibration response amplitudes； when the initial tension of the conductor increases from 16 to 26 kN， its horizontal and vertical amplitudes are decreased by 31.1% and 23.4%， respectively. When the line damping ratio increases from 0.02 to 0.15， the conductor's horizontal and vertical amplitudes are decreased by 36.4% and 44.2%， respectively. Increasing the initial tension and damping ratio effectively suppresses wind-induced vibrations of the lines. This study reveals the collaborative mechanism of mountain wind field acceleration effects and tower-line dynamic coupling， quantitatively evaluating the impact of key parameters on line wind-induced vibration. The proposed initial tension optimization and damping ratio enhancement measures provide important technical support for the wind-resistant design of transmission lines in mountainous regions.