PurposeTo evaluate the occurrence and influencing factors of myopia occurrence in pre-myopia children aged 3–6 years. MethodsThis study included 204 pre-myopia (-0.50D<spherical equivalent (SE) ≤+0.75D) children with three years follow-up in Beijing Hyperopia Reserve Research. All participants underwent a comprehensive eye examination. The length of macular Bruch's membrane (BM) and the temporal vascular arcade angle were measured upon fundus photographs. ResultsMean age at initial visit was 4.28 ± 0.98 years and mean SE was 0.45 ± 0.29D. Both at baseline and after 3 years of follow-up, axial length was longer in boys than that in girls. (all P < 0.001) Children were divided into two groups according to the refractive status of children at the final follow-up: Myopia group (SE≤-0.50D) and Non-myopia group (SE>-0.50D). The length of macular BM was shorter in Myopia group than that in Non-myopia group (P < 0.001). Baseline SE and the length of macular BM were independent influencing factors which associated with myopia occurrence (OR, 0.031; 95 % CI, 0.008–0.117, P < 0.001 and OR, 0.204; 95 % CI, 0.055–0.763, P = 0.018, respectively) by multivariate binary logistic regression analysis. SE changing process represented the changes of SE, Myopia group had bigger SE changes (P < 0.001). And in the multivariate liner regression analysis, age was the common influencing factor of SE changing process in total participants, Non-myopia group and Myopia group (B = 0.234, P < 0.001; B = 0.078, P = 0.010; B = 0.161, P = 0.046, respectively) ConclusionsInitial SE and the length of macular BM in pre-myopia children aged 3–6 years were the independent factors of the occurrence of myopia. And initial age was the common factor that associated with SE changing process.