AIM: To observe the effect and security of applying mitomycin C (MMC) in Epi-LASEK surgery of middle or high myopia. METHODS: The 406 eyes underwent Epi-LASIK surgery were randomly divided into MMC group (203 eyes) and control group (203 eyes). Automatic rotational Epi-LASIK, which had features of a blunt oscillating blade, was used to make epithelium flap. Visx star S4 excimer laser was used for myopia. 0.2g/L MMC solution was covered on the corneal stroma bed after the laser ablation in MMC group. Refractive diopter determined keeping time. The eyes in control group received the same thing as MMC group except MMC. The other operate were identical. The postoperative symptom, epithelial flap, incorrect visual acuity, dioptersand, haze formation were recorded. RESULTS: All of surgery had been finished successfully. The period of follow-up ranged from 6 months to 2 years. Stimulate formation were light in two groups. It often happened in the first day and got better in the second day. On the third day of postoperative, 15 eyes had I-II level stimulate formation in MMC group and 13 eyes in control group. There was no statistically significant difference between two groups (P>0.05). The corneal epithelia healed up within 3-5 days in all patients, with no significant difference between two groups (3.78±0.75 vs 3.55±0.89, t=1.522, P>0.05). Epithelial flaps of 191 eyes (94.1%) in MMC group were well healed when took off the lens for 3-5 days and 198 eyes (97.5%) in control group. Six month after surgery, 195 eyes (93.6%) in MMC group acquired satisfactory visual and 172 eyes (847%) in control group. There were statistically difference in two groups (P<0.05). Refractive regressions quantity of 11 eyes (5.4%) in MMC group was up to -0.50D in 6 month after surgery and 23 eyes (11.3%) in control group. 167 eyes(82.3%) in MMC group suffered 0 level haze while 125 eyes (61.6%) in control group. There were statistically difference (P<0.05). CONCLUSION: The application of 0.2g/L MMC during Epi-LASIK is proved to be a safe and effective method for middle or high myopia. It can reduce the formation of haze and prevent UCVA falling.