Abstract: The stay cable is one of the main force members of cable-stayed bridges, and the study of its aerodynamic characteristics is the basis for the study of the aerodynamic characteristics of the overall structure. In order to explore the Reynolds number effect of aerodynamic force of stay cable with smooth surface, the wind tunnel pressure measurement test of stay cable section model under different wind speeds was carried out under uniform incoming flow, and the variation law of mean drag coefficient and mean wind pressure coefficient of cable-stay with Reynolds number was obtained. The results show that the mean aerodynamic coefficient of the stay cable with smooth surface has different performance in different Reynolds number regions. The mean drag is stable at 1.2 and 0.6 in the subcritical Reynolds number region and the supercritical Reynolds number region, respectively. The mean lift coefficient is 0. The mean drag coefficient decreases rapidly in the critical Reynolds number region. Correspondingly, the mean lift coefficient increases from 0 to the maximum and then decreases to 0. For the fluctuating aerodynamic force, the value of the fluctuating lift in the subcritical Reynolds number region is much larger than the fluctuating drag, which means that the cross-wind excitation of the stay cable is much larger than the along-wind excitation. The distribution of the mean wind pressure coefficient experienced a symmetric-asymmetric-symmetric variation process with the increase of Reynolds number, which reflected the variation law of laminar separation, unilateral turbulent separation and bilateral turbulent separation, and was a qualitative response to the variation trend of the mean lift coefficient. The variation trend of the absolute value of the mean base pressure coefficient at the back pressure of the stay cable was consistent with the mean drag coefficient.