Abstract: The aerodynamic-damping and frequency characteristics of a launch vehicle with boosters vibrating in the first free-free bending mode, and the influence of the reduced frequency on aerodynamic damping were experimentally studied in a transonic wind tunnel. The test Mach number ranged from 0.70 to 1.05, and the angle of attack ranged from 0° to 10°. The result shows that for the elastic model with boosters, the aerodynamic damping and modal frequency are affected by the angle of attack while the trend is not obvious. The aerodynamic damping changes with the Mach number. The transonic dip appears near the Mach number of 0.90. The modal frequency of the first mode decreases with the increase of the Mach number. The reduced frequency has some effect on the aerodynamic damping that when Mach number ranged from 0.70 to 0.90 and after 1.00, the aerodynamic damping decreases with the increase of the reduced frequency, while Mach number ranged from 0.92 to 0.98, the aerodynamic damping increases with the increase of the reduced frequency.