Wind tunnel testing methods were employed to study the interference effect and drag coefficients of multi-bundled conductors under various azimuths. Drag coefficients of isolated conductor and circular cylinder with the same diameter were compared under various wind velocities and turbulence intensities. The drag coefficients of sub-conductor and total drag coefficients of multi-bundled conductor were obtained and their results are compared with those obtained from Codes and other researchers. The results show that the drag coefficient of the isolated conductor is 13% less than that of the circular cylinder under high velocity, indicating that the twisted shape can reduce the drag coefficient of the circular cylinder. When two sub-conductors are in front-back arrangement, the drag coefficient of the back sub-conductor decreases significantly, and the less distance between them, the more the drag coefficient decreases. The total drag coefficient of multi-bundled conductors is small under certain azimuth when the significant interference effect is considered. The enveloped drag coefficients of multi-bundled conductors with 23.94 mm in diameter and 400 mm in distance are recommended as 1.02, 1.00, 0.97 and 0.93 for isolated conductor, two-bundled conductor, four-bundled conductor, six-bundled conductor and eight-bundled conductor, respectively.