To investigate the effects of different laser in situ keratomileusis(LASIK) ablations on clinical outcomes and corneal asphericity. METHODS: Totally 48 cases (95 eyes) were treated by LASIK, with 45 eyes using Q-value guided ablation (aspherical ablation), and 50 eyes using non-Q-value guided ablation. Visual acuity (VA), refraction, keratometry, Q-value, spherical aberration and contrast sensitivity function (CSF) were assessed at 1, 3 and 6 months after operation. RESULTS: There were no statistically significant differences in VA and refraction between the two groups after surgery. The rate of refraction within 0.50D was 95% for Q-value group and 90% for non-Q-value group at postoperative 3 months, with 97% and 98% at 6 months. The postoperative CSF was elevated in Q-value group, whereas no difference between preoperation and postoperation in non-Q-value group. The average Q-value was about -0.18 for both groups before the surgery, and after the surgery it was about 0.50 for Q group and 0.80 for non-Q group. The postoperative 6 months spherical aberration increased to 4 times in Q-value group and 8.5 times in non-Q-value group compared to preoperation. There was a tight relation between ⊿Q and attempted refraction, without relation between ⊿Q and age, gender, preoperative keratometry, Q-value and spherical aberration. The formula obtained through curve fitting was y=0.18e^0.32x，R² = 0.72，for non-Q-value group, and y= 0.04x²-0.19x+0.54，R²= 0.75, for Q-value group(y:⊿Q, x: attempted refraction). CONCLUSION: Compared to non-Q-value guided ablation, Q-value guided ablation of LASIK for treating myopia can reduce destroy on corneal asphericity, causing less increment in spherical aberration and improving visual quality after the surgery. But it still had a distance between the expected and the actual postoperative Q-values. The postoperative increment of Q-value was tightly related with attempted refraction."