AIM:To study the relevant factors of the forward shift of posterior corneal surface (Diff value) in myopia after excimer laser in situ keratomileusis (LASIK). METHODS:120 myopic patients (240 eyes) who underwent LASIK were included in this study. Posterior Diff value were obtained in Orbscan-Ⅱcorneal topography before and 1,3,6,12 months after the surgery. Multiple regression analysis was used to assess the factors that affect the posterior Diff value. RESULTS:Factors relevant to the forward shift of the posterior corneal surfaces were ablation percentage and preoperative posterior Diff value,and intraocular tension was also the factor at 1 month after the surgery.CONCLUSION:Preoperative posterior Diff value,and the ablation percentage must be controlled in the condition the effect of the surgery could be guaranteed. At the same time monitoring the intraocular tension after LASIK is also important,and if necessary,reduce it to avoid some complications after LASIK.