Abstract: Because the characteristics of wind field in hilly terrain are obviously different from that in flat terrain, the effect of hilly terrain wind field should be considered when analyzing the wind-induced vibration response of the tension suspension-braced transmission structure in hilly terrain.To investigate the wind-induced response characteristics of this structure under hilly terrain conditions, a study is conducted on the characteristics of the wind field over the hill based on wind tunnel test results. Emphasis is placed on the systematic evaluation of how slope and height of hills influence the variations of both mean and fluctuating wind speed, and calculation models for the speed-up ratios are developed. A nonlinear analytical framework is established to evaluate the wind-induced vibration of the transmission structure, explicitly incorporating the effect of the wind field over the hill. Based on the proposed framework, the wind-induced vibration response is analyzed for a two-span section of tension suspension-braced transmission structure in hilly terrain. The results indicate that: with the increase of the slope and height of hill, the mean velocity speed-up ratio at the crest gradually increases, and at the foot of the leeward side, the mean velocity speed-up ratio gradually decreases, while the fluctuating velocity speed-up ratio significantly increases.Considering the effect of hilly terrain wind field, the mean value of the midpoint lateral displacement of conductor and supporting-conductor suspension cable decreases greatly, respectively around 20% and 12%, while the mean value of the midpoint tension changes by around 2%. Under the influence of the fluctuating velocity speed-up effect, considering the effect of hilly terrain wind field, the standard deviation of the midpoint lateral displacement and midpoint tension of the conductor and supporting-conductor suspension cable is increasing, with the maximum increase in the conductor midpoint tension, which can reach 14%.