Objective  To investigate the characteristics and relevant factors of intraocular straylight before and after sub-Bowman′s keratomileusis (SBK). Methods  This was a prospective clinical study. Straylight measurement was performed on 46 myopic and myopic astigmatism patients (92 eyes) before SBK surgery and 1 day， 1 week， and 1 month after surgery using Oculus C-Quant straylight meter. In 46 patients， there were 29 males and 17 females， the mean age was (24.0±5.4)years (range： 18 to 39 years)， and the mean preoperative spherical equivalent (SE) of refraction was (-6.70±1.50)D (range： -11.13 to -4.75 D)， with mean astigmatism of (0.68±0.58)D (range： 0 to 2.50 D). The mean keratometric value and central corneal thickness (CCT) were tested by Pentacam device. The data was analyzed for statistical significance by repeated measure ANOVA， paired t tests and Pearson correlation using SPSS 13.0 software. Results  Patients had a mean straylight of logarithmic value of the straylight parameter [log(s)]=(0.90±0.13) before surgery， which showed no significant correlation with spherical equivalent (SE)， keratometric (K) value， and CCT. After surgery， the mean straylight of [log(s)]=0.96±0.13， 0.98±0.10， and 0.99±0.09 at 1 day， 1 week， and 1 month postoperatively respectively. When comparing with preoperative straylight values， the difference did reach a statistical significance increase for various time points after SBK (F=24.94， P＜0.05). The individual postop-preop changes in straylight showed significant negative correlation with the preoperative values (r=-0.47， -0.67， -0.78， P<0.05)， and showed no significant relationship with intended refractive correction and ablation depth. Conclusion  Straylight values increases significantly at early time after SBK， which maybe influence visual performance at this time. Patients with lower preoperative straylight values present exacerbated elevation after SBK.