Aiming at fulfilling the requirement of 25 Hz high scanning frequency of the airborne whiskbroom scanning spectrometer, a swing mirror with three reflectors is designed. Firstly, by revealing the relationship between the reflection area and the deviation of the rotation axis and comparing performance of several swing mirrors with the different numbers of reflectors. The arrangement of three reflectors around the rotation axis of swing mirror was adopted. Thus rotating at a speed of 600 r/min the mirror was able to achieve 1 800 scans within a single minute. At the same time, the swing mirror used uniform rotation to reduce the difficulty in controlling and improve the stability of the sweep-scanning system. Through topology optimization and integrated optimization, the weight of the swing mirror was reduced to 5.28 kg and the lightweight ratio was 58%. Finally, calculated by the finite element simulation, the RMS of the reflector was better than λ/20 in 1 g gravity and centrifugal force at 600 r/min rotate speed environment and the fundamental frequency is 1 199 Hz. This verifies that the swing mirror is of high mechanical stability. It can satisfy the higher scanning frequency requirement of airborne whiskbroom scanning spectrometer.