The transmission line breaking across high-speed railway is one of the important factors affecting the safety of power system. In this paper，the finite element model of transmission lines across high-speed railway sections is established to analyze the flow field disturbance in the process of high-speed train crossing the lines； wind load and dynamic characteristics of transmission lines are calculated. The vibration response characteristics of transmission lines in time domain are studied by numerical simulation method，and the influences of speed and length of train are considered. The vibration response characteristics of transmission lines in time domain are verified by field measurement. The results show that the flow field disturbance caused by high-speed train crossing will cause line vibration for more than 10 s，and the vibration frequency is close to the line modal natural vibration frequency，which is easy to cause line resonance. The vibration of the line can be reduced by increasing the height of the line and decreasing the span length of the line. The results of this paper are of great significance to the in-depth study of the structural design theory of transmission lines across high-speed railways.