Objective To evaluate the accuracy of the axial length/corneal radius (AL/CR) ratio in the diagnosis of myopia in adolescents and children. Methods This retrospective clinical study included 1 011 consecutive adolescents and children with refractive errors, aged 3 to 17 years old, who visited the Department of Ophthalmology, Shanghai Children′s Medical Center from December 2012 to September 2014. All subjects underwent measurements for distance vision, axial length (AL), the average radius of the corneal curvature (CR), cycloplegic refraction, etc. Then the AL/CR and spherical equivalent (SE) from cycloplegic refraction were calculated. SE≤-0.50 D was defined as myopia, AL/CR>3 was defined as suspect myopia. Results The median AL/CR was 3.05(2.27, 3.54), the median SE was -1.25 D(-11.38 D, +11.63 D). There was negative correlation between SE and AL/CR (r=-0.563, P<0.01). Sensitivity was 0.896, specificity was 0.918, and accuracy was 90.3%. The area under the ROC curve was 0.965 (P<0.01). The Kappa coefficient was 0.790, where SE was defined as the gold standard. Conclusion The AL/CR ratio is highly accurate in the diagnosis of myopia in adolescents and children.