Objective To evaluate the direction and degree of dynamic cyclotorsion during laser in situ keratomileusis(LASIK). Methods This retrospective study comprised 235 eyes of 133 patients that had LASIK for myopia with or without astigmatism by Schwind Amaris excimer laser.According to eyes, preoperative diopter of spherical power were divided into groups, dynamic cyclotorsion was assessed during LASIK.Enumeration data were compared with independent samples test. Results Dynamic cyclotorsion degree range from 0° to 7.88° (absolute value). Dynamic cyclotorsion degree of right eyes range from 0° to 7.77° (absolute value)the mean AP was 1.74°±1.46°. Dynamic cyclotorsion degree of left eyes range from 0° to 7.88°(absolute value)the mean AP was 1.90°±1.54°. There was no significant statistical difference between right eyes and left eyes (t=0.69, P=0.25). 235 eyes were successful measured.26 eyes(11.06%) had incyclotorsion, range from 0 degrees to 7.88 degrees, the mean AP was 2.03°±2.05°; 12 eyes (5.11%) had excyclotorsion, range from 0.18 degrees to 6.81 degrees, the mean AP was 2.16°±1.87°; 197 eyes(83.83%) had both excyclotorsion and incyclotorsion, range from 0.01 degrees to 5.79 degrees. the mean AP was 1.74°±1.34 °. The dynamic cyclotorsion range from 0.01 degrees to 2.24 degrees, the mean AP was 3.54°± 2.00°.The dynamic cyclotorsion amplitude of right eyes was 3.26°±1.65°, left eyes was 3.33°±1.71°. There was no significant statistical difference between right eyes and left eyes(t=0.93, P=0.20). Cyclotorsion amplitude had been compared : high-diopter>mid-diopter>low-diopter. There were statistical differences between three groups(t=4.10, P=0.001; t=3.04, P=0.002; t=6.06, P=0.001). Conclusion Dynamic cyclotorsion occurs during LASIK.The higher myopic degree is, the larger the eye cyclotorsion degree and the total amplitude will be.So Dynamic cyclotorsion should be measured and compensated. Key words: Laser in situ keratomileusis(LASIK); Dynamic cyclotorsion