Objectives: To measure choroidal thickness (CT) in highly myopia eyes using enhanced depth imaging spectral-domain optical tomography (EDI SD-OCT) and explore the relationship between the CT and axial length (AL) and corneal curvature. Methods: This study assessed 66 eyes of 33 patients with both eyes of high myopia (equivalent sphericity >=-6D or AL >= 26mm) who underwent treatment at the department of ophthalmology, fourth hospital of Hebei Medical University from August 2020 to August 2021(High-myopia group). The control group included 54 eyes from 27 healthy volunteers. The patients in the two groups were 18 similar to 40 years old. EDI SD-OCT was used to measure the CT of subfoveal choroidal thickness (SFCT) and CT from fovea to nasal and temporal sides at an interval of 500 similar to 2500 mu m. The intraocular pressure, diopter, ocular axis, corneal curvature, and CT were compared between the two groups. The correlation between CT, diopter and AL was measured by Pearson's r. Results: The diopter, AL, vertical corneal curvature, and CT in the high-myopia group were significantly higher than those in the control group (P<0.05). There was significant correlation between SFCT and AL in both groups (P<0.05). There was a negative correlation between AL and CT in high-myopia group (r=-0.395, P<0.05), and a positive correlation between AL and CT in control group (r=0.29, P<0.05). There was a weak correlation between AL and gender, intraocular pressure, and horizontal corneal curvature(P<0.05), and a negative correlation between AL and diopter (r=-0.861, P<0.001). Conclusion: EDI SD-OCT can quantitatively measure the CT of high myopia. The CT of patients with high myopia was significantly thinner than that of the control group of the same age. There was a significant correlation between diopter, AL and CT, suggesting that AL is a parameter indicating the degree of myopia, and the change of CT may play a role in the occurrence and development of high myopia.