Objective To evaluate the changes in visual acuity and reaction times at different contrast levels in myopic patients before and after sub-Bowman′s keratomileusis （SBK）. Methods This was a prospective self-control study. A total of 20 patients （40 eyes） who had undergone SBK were enrolled in this study. LogMAR contrast visual acuity and reaction times were measured by the multi-functional visual acuity tester （MFVA-100） at 4 contrast levels （100%， 25%， 10%， 5%） with a dark background in a dark environment before surgery and 1 month and 3 months after surgery. Data were analyzed using ANOVA and SNK. Results At the same room illumination， logMAR values gradually increased as contrast levels decreased. The postoperative logMAR values at 100% and 25% contrasts were significantly lower than preoperative values （q=4.722， 5.167， P<0.05； q=3.000， 3.217， P<0.05）， but the differences were not significant at 10% and 5% contrast levels （F=1.647， 1.382， P>0.05）. Reaction time increased with decreases in contrast levels. The postoperative reaction times became shorter at contrast levels of 100%， but were longer at 25%， 10% and 5% contrast levels. The differences were not significant （F=0.484， 0.049， 1.073， 0.637， P>0.05）. Conclusion After SBK， the logMAR values at 100% and 25% contrast levels were reduced， but there were no significant differences at 10% and 5% contrast levels. The surgery has no effect on reaction times at the 4 contrast levels. Myopic patients can acquire good contrast visual acuity in a dark environment after SBK. Contrast visual acuity and reaction time may be used as one of the bases to evaluate the effects of the surgery.