AIM:To observe the effect of mitomycin C(MMC) in middle and high myopic laser subepithelial keratomileusis(LASEK).METHODS:Totally 166 cases (332 eyes) with myopia were randomly divided into observation group with the use of 0.2g/L MMC and control group without the use of MMC ,83 cases (166 eyes) in each group. All patients were followed-up 12 months and the corneal epithelial healing time, the uncorrected visual acuity as well as the occurrence of corneal haze after surgery were observed.RESULTS:The corneal epithelial healing timewas 4.05±0.30 days in the observation group and 4.22±0.37 days in the control group, there was no significant difference between the two groups (P＞0.05). In postoperative 12 months, there were 17 eyes whose uncorrected visual acuity were ＜0.8, 42 eyes were 0.8-1.0 and 107 eyes were ≥1.0, the percent in each section of the two groups had no significant difference between groups (P＞0.05). The incidence of haze ≤1 or 2 grade was 1.8% (3/166 eyes) in observation group and 2.4% (4/166 eyes) in control group with the preoperation diopter was≤-6.00DS, there was no significant difference between the two groups (P＞0.05). While the preoperative diopter was -6.00--8.00DS, the haze rate was 3.0% (5/166 eyes) in observation group and 10.2% (17/166 eyes) in control group, there was significant difference between groups (P＜0.05). When the preoperative diopter was ≥-8.00DS, the haze rate was 6.0% (10/166 eyes) in observation group and 17.5% (29/166 eyes) in control group, there was significant difference between groups (P＜0.05). CONCLUSION:Application of MMC in LASEK can reduce the incidence of postoperative haze effectively with high safety.