Abstract: Models of stay cable sections and a corresponding drag coefficient testing system were designed to investigate the effects of cable surface pattern, inclination and yaw angles, and wind turbulence intensity on drag coefficient of the stay cables under 3D wind flows. Wind tunnel test indicates that the drag coefficient increases with an increase in the inclination angle when the yaw angle is about 0°, but it has a little change when the yaw angle is about 90°. The drag coefficient of dimpled cables or cable with helical strakes increases about twice compared with that of smooth cables, and the greater the ratio of dimpled area to the whole surface area and the higher the helical strakes, the larger the drag coefficient. The turbulence intensity has significant effect on the drag coefficient for a smooth cable.