Myopia is a common cause of visual impairment worldwide. Choroidal thickness (ChT) reflects the characteristic changes in myopic children and may be used as an important index of myopia. The purpose of this study was to investigate ChT and its distribution across the posterior pole in young myopic Chinese patients using enhanced depth imaging optical coherence tomography (EDI-OCT) and to explore the factors associated with it. A total of 402 myopic Chinese patients aged 6-16 years who underwent complete ophthalmic examinations, including those for axial length, cycloplegic refraction, and intraocular pressure, were examined with EDI-OCT. The mean subfoveal ChT was 303.08 ± 76.87 m and displayed large variations at different positions ( < 0.05). The thickest sector was located 3 mm temporally from the fovea. Multivariate regression analysis showed a significant negative correlation of the subfoveal ChT values with axial length (AL), whereas the ChT was moderately influenced by the patient's sex. AL accounted for 7.9% of the ChT variance, whereas sex explained 9.6% of the ChT variance. In the population aged 11 years and older, AL accounted for 13.1% of the ChT variance. However, in those younger than 11 years, age was the only significant explanatory factor accounting for 5.2% of the ChT variance. In conclusion, we found a significant decrease in ChT with age in myopic children younger than 11 years. The negative association between age and ChT in children aged 11 years and older may be offset by the choroidal thickening mediated by pubertal growth spurts. The positive correlation between ChT and spherical equivalent in myopic adolescents aged 11 years and older suggests that the protective effect of lens thinning against rapid axial elongation disappears with age. Axial elongation becomes the dominant determinant of ChT in this age group.Copyright © 2020 Fen Xiong et al.