Objective: To study ablation error and its central corneal thickness variations in patients with myopia after small incision lenticule extraction (SMILE), and to investigate the influence of low, moderate and high myopia on central corneal ablation error. Methods: This was a retrospective case-control study. Sixty-one myopic patients (a total of 120 eyes) who had undergone SMILE surgery from January 2017 to August 2017 at the Eye Hospital of Wenzhou Medical University were chosen for the study. Data were organized by refractive status into low (24 eyes, -0.50 D≤low myopia≤-3.00 D), moderate (54 eyes, -3.00 D < moderate myopia ≤-6.00 D), and high (42 eyes, high myopia > -6.00 D) myopia groups. The central corneal thickness (CCT) of patients undergoing SMILE was measured by the Sirius anterior segment analysis system preoperatively and postoperatively at 1 month and 3 months. Among different myopia groups, the ablation error was calculated simultaneously during each visit and was defined as the difference (△CCT) between actual central corneal ablation thickness (A-CCT) and the predicted central corneal thickness (P-CCT). The difference ratio of △CCT (defined as △CCT/P-CCT) and the relationship (in diopters) between △CCT, CCT, and ablation diameter were analyzed. Data were analyzed with a paired-samples t-test, ANOVA, Kruskal-Wallis H test, and Pearson correlation analysis. Results: Among the three myopia groups, results for A-CCT were all less than the P-CCT, and the differences in △CCT between any two groups were found to be statistically significant (F=21.047, 35.100, all P < 0.001). No significant difference was found in the difference ratios of △CCT among the three groups. The △CCTs of the low, moderate, and high myopia groups were -8.9 ± 5.0 μm, -15.6 ± 6.2 μm, -21.4 ± 5.9 μm, respectively. The differences between A-CCT and P-CCT were significant (t=8.67, 18.50, 23.65,P < 0.001). Moreover, there were significant correlations both in the relationship of corneal ablation error with preoperative refractive status and ablation diameter after SMILE surgery (r=0.649, 0.384, all P < 0.001). However, SMILE surgical ablation error and preoperative corneal thickness had a negative correlation (r=-0.219, P=0.016). Conclusions: A-CCT in low, moderate and high myopia groups after SMILE surgery is less than the predicted thickness. △CCT increases as the degree of myopia increases. There are significant differences in △CCT between different myopia groups, nevertheless the difference ratio of △CCT basically remains consistent.