Objective To evaluate the treatment of undercorrection after the excimer laser in situ keratomileusis (LASIK) for correcting moderate and high myopia. Methods An enhancement ablation was performed in 48 eyes of 39 patients who had undergone LASIK but remained in undercorrection. Four procedures were performed within 1 month postopoeratively, and the others performed between 3 and 10 months. The surgical technique includes the re-invert of the ceal cap from the temporal side, the excimer laser ablation, and the re-position of the cap.Results The undercorrection (spherical equivalent) ranged from -2.00 to -11.00 D, with a mean of -4.34D±1.95 D. Following up after enhancement ablation was done after 4 to 12 months, the refractions in the 42 eyes were found to be within ±1.00 D. Undercorrection of -2. 50 D to -5.00 D recurred in 6 eyes. Uncorrected visual acuity equals to the preoperative spectacle corrected visual acuity in 39 of 48 eyes (81.3%). Five eyes gained 1 line, 1 eye gained 2 lines and 4 eyes lost 1 line. No eyes had haze.Conclusion Undercorrection after LASIK can be corrected by an enhancement ablation of the stroma under the primary ceal cap with a 193 nm ArF excimer laser, and the time for the enhancement of ablation is at 3 months postoperatively.