Objective To study the cause of the big kappa angle.Methods Twenty-seven eyes were measured with kappa angle, central corneal thickness, white-to-white corneal horizontal diameter, and the optic disc-macular distance.Results The mean kappa angle of the abnormal big kappa eyes was 9.48±2.24°, the optic dise-macular distance was 5.08±1.33mm, mean central corneal thickness was 580.58±53.01 um, mean corneal horizontal diameter was 12.13±0.51mm, Which were bigger than the normal eyes.Conclusions Several abnormal structural factors are found in the big kappa angle eyes, which maybe the cause of the big kappa angles.