Objective To Compare the astigmatic results between circular vacuum aspiration rings and oval vacuum aspiration rings in Sub-Bowman's Keratomileusis (SBK).Methods It was a retrospective case controlled study.A total of 51 patients (102 eyes) who underwent SBK in the West China Hospital.Either circular vacuum aspiration rings or oval vacuum aspiration rings were chosen to make the corneal flaps.Circular vacuum aspiration rings were used in 49 eyes and oval vacuum aspiration rings were used in the other 53 eyes.Corneal curvature was measured with corneal topography and was used to calculate the astigmatic values.An independent samples t test was used.Results The astigmatic values 1 week after surgery for the oval vacuum aspiration ring group were -0.90±0.54 D and-0.84±0.71 D for the circular vacuum aspiration ring group.Astigmatic values change before 1 week after surgery in the oval vacuum aspiration ring group was 0.58±0.77 D and was 0.57±0.76 D in the circular vacuum aspiration ring group.There was no significant difference between the two groups.No complications were detected that would significantly affect visual acuity during or after surgery.Conclusion These results suggest that oval vacuum aspiration rings in SBK will not increase the induced astigmatism.