Objective：This study aims to provide basis for prevention and control of myopia by analyzing the prevalence of myopia and refraction-related ocular biological parameters of teenagers in 4 primary schools in Nanjing. Methods：By using random cluster sampling method，217 first-grade students from 4 primary schools in Nanjing were selected to carry out a follow-up study for 6 consecutive years. Results：After 6 years of follow-up，the prevalence rate of myopia increased from 6.70% to 72.63%. The number of moderate myopia increased gradually. The proportion of moderate myopia increased from 8.33% to 52.31%. there were 124 of 167 non-myopia students at baseline developing into myopia during the 6 years，and students in grade 3 to 4 or grade 5 to 6 have a higher incidence rate. AL/CRC increased from 2.89±0.08 to 3.13±0.14（P＜0.05）. SER was correlated with logMAR，AL and AL/CRC（Except for grade 1）（P＜0.05）. Conclusion：The prevalence rate of myopia increases gradually in 4 primary schools in Nanjing，and the moderate myopia increases dramatically. Grade 3 to 4 and grade 5 to 6 are the peak stages of myopia. SER correlates with logMAR，AL and AL/CRC. AL/CRC can acts as an evaluation index for myopia screening.