Based on the Computational Fluid Dynamics（CFD）method，the lateral and vertical average wind speeds of transmission lines on the windward side of the mountain ranges are obtained，and the effects of three factors，which are the line erection location，tower nominal height，and mountain slope，on the wind speed of transmission lines are studied. The finite element model of the four-span transmission line across the mountain range is established. The wind-induced swing response of the line is calculated using the mountain wind speed and the flat wind speed respectively，and the percentage increase of the wind-induced swing angle is therefore obtained. The quadratic regression equation of the three factors and the percentage increase of wind-induced swing angle are also built by using the response surface method（RSM）. The studies show that，with the line closer to the ridge，the towel nominal height will get higher，and the line’s wind-induced swing also becomes more severe. For the lines erected below 3/4 of the total height of the mountains，the wind speed can be appropriately reduced during the design process，which not only ensures the safety of the line’s wind-induced swing，but also improves the economy. As for the lines erected above 3/4 of the total height of the mountains，the designed wind speed should be appropriately increased in order to improve the safety of the wind-induced swing of transmission lines.