Wind-induced responses of a 500kV single-circuit transmission tower are computed based on wind forces acting on the tower obtained from wind tunnel tests using high-frequency-force-balance technique in a wind tunnel and the modal decomposition method. The results show that the dynamic displacements，accelerations and base bending moments (BBM) are all large in both along and across wind directions, and furthermore, the across wind dynamic responses are generally larger than the along wind responses. The first mode has dominant contributions to the total responses respectively in both A and B directions. In addition, gust response factors corresponding to displacement and BBM have similar trends. The maximum displacement gust response factors of critical nodes are no more than 1.8, and the maximum moment gust response factors are about 1.5.