Abstract: Objective To investigate the variation of visual acuity (VA) at different contrast levels under dark background in selecting aviation cadets, and to provide reference data for visual function evaluation of cadets with lens opacity. Methods One hundred and sixteen aviation candidates (232 eyes) with normal VA were enrolled. LogMAR VA was measured at 4 contrast levels (100%, 25%, 10%, 5%) under dark background with multi-functional visual acuity tester (MFVA-100). The logMAR VA at different contrast levels and the difference between the logMAR VA under dark background was analyzed. Results With contrasts of 100%, 25%, 10%, and 5%, logMAR, VAs were -0.118(0.127), 0.098(0.190), 0.360(0.204), 0.680(0.228) in right eye, respectively, and, respectively in left eye were -0.098(0.109), 0.087(0.160), 0.333(0.148), 0.645(0.238). VA decreased gradually with the decrease in the contrast level (P< 0.01) and had no statistically significant difference between right and left eye at the same contrast level (P> 0.05). The difference of the logMAR VA in right eye between contrast 5% and 10% was 0.333(0.190), and it was 0.453(0.135) between contrast 10% and 100% and 0.212(0.096) between contrast 25% and 100%, and, in left eye was 0.360(0.124) between contrast 5% and 10%, 0.427(0.132) between contrast 10% and 100% and 0.213(0.100) between contrast 25% and 100%, the difference of the logMAR VA among different contrast had no statistically significant difference between right and left eye (P> 0.05). Conclusion In the medical selection of aviation cadets, contrast visual acuity was scientific and reliable for visual function evaluation in cadets with lens opacity.