Abstract: Fluctuating wind speed spectrum is one of the important parameters for accurately calculating wind-induced responses of transmission towers located in high altitude regions. Based on field observation study on fluctuating wind on an open terrain site at an altitude of 4 500 m, 206 sets of fluctuating wind speed samples with 10 min average wind speed exceeding 19 m/s are obtained. The power spectrum curves for longitudinal fluctuating wind speed of 206 samples are determined by Pwelch power spectrum estimation function. The dimensionless normalized mathematical expression of wind speed spectrum is determined by nonlinear fitting method, and the energy-frequency distribution characteristics of fluctuating wind in high altitude regions are revealed. The observation spectrum is compared with some typical standard spectrum. Davenport spectrum can better predict the energy distribution of the measured fluctuating wind in high altitude regions, but may underestimate the measured wind field energy at low frequency range. The resonance response term of the transmission tower is derived based on the fitted wind speed spectrum measured in high altitude regions, and the influence of the measured fluctuating wind speed spectrum and Davenport spectrum on the resonance response and wind-induced vibration coefficient are analyzed. The resonance response term and the overall wind-induced vibration coefficient calculated by the measured spectrum are lower than the calculated values by Davenport spectrum, and the relative difference of the resonance response term is about 19%. The relative difference of wind-induced vibration coefficient is 2.7%~4.0%, and it increases approximately with the height of the tower.