Abstract: The level of aerodynamic design is not only one of the important indicators to evaluate the progressiveness of aircraft, but also the key to improve the competitiveness of large passenger aircraft. The main objectives include increasing lift and reducing drag. In order to meet the practical needs of engineering applications, this paper develops a non-contact measurement technology that can be used to evaluate and measure the drag reduction effect of small ribs in flight tests at high Reynolds number. The results show that the airflow flowing through the small rib is faster, the mechanical energy loss is less, and the flow friction of the small rib is smaller. In addition, the small rib suppresses the spanwise component velocity pulsation, and it is speculated that the spanwise strip strong pulsation area distributed downstream of the small rib is related to the flow direction vortex generated by the airflow flowing through the small rib. On this basis, the flow drag reduction effect of the small rib and the suppression of spanwise velocity pulsation can be interrelated.