Abstract: Objective To investigate the variation of visual acuity (VA) at different contrast levels under bright background in military helicopter fight cadets. Methods Eighty-six military helicopter fight cadets (172 eyes) with normal VA were enrolled. logMAR VA was measured at 4 contrast levels (100%, 25%, 10%, 5%) under bright background with multi-functional visual acuity tester (MFVA-100). The relationship of VA at different contrast levels under bright background was analyzed. Results logMAR VA of 100%, 25%, 10%, and 5% in right eye were -0.001±0.128, 0.257±0.152, 0.537±0.158, 0.726±0.174, respectively; logMAR VA of 100%, 25%, 10%, and 5% in left eye were 0.003±0.127, 0.248±0.156, 0.521±0.170, 0.706±0.197, respectively. Visual acuity decreased gradually with a decrease in the contrast level, and it was significantly better at high contrast than that at low contrast (P< 0.05). Visual acuity (VA) was of no statistically signifcant difference between right and left eye in the same contrast level (P> 0.05). Visual acuity at 100% contrast was linearly related to the visual acuity at 25%, 10%, 5% contrasts respectively (P< 0.05). Conclusion The different contrast levels signifcantly affect contrast visual acuity. The lower the contrast is, the larger visual acuity changes.