Due to the limitation of wind tunnel test capability, it was very hard to be completely consistent with the actual flight of high speed aircraft. As an important similarity number, Reynolds number had been used widely in classical fluid mechanics wind tunnel experiments. It had a significant impact on establishing aero-optical similarity standard to study the influence on aero-optics induced by Reynolds number. Based on the ∏ theorem, the possible variables that affected aero-optics were analyzed, which verified Reynolds number was a similarity standard value of aero-optics. A creative experimental equipment was designed to realize the unit Reynolds number ranging from 106-108 m-1. Eight typical Reynolds numbers were chosen, BOS-WS (BOS-based Wavefront Sensor) technique was used to measure the corresponding optical path difference. Based on the function curve fitting method, the power function between Reynolds number and the rms of the optical path difference was acquired. The measured results with different sizes were compared. It could be found that, for the two dimensional supersonic film, the acquired law was not affected by the size of the observed aperture.