Objective: To analyze the distribution of uncorrected visual acuity in children and adolescents aged 3-18 years with relative safe refractive range, and to develop the growth curve and reference range of uncorrected visual acuity in children and adolescents of different ages, so as to provide reference for formulating the referral threshold for myopia screening practice. Methods: Using cluster sampling method, 9 146 children and adolescents aged 3-18 years old in Shanghai were selected for uncorrected visual acuity, cycloplegic refraction, slit lamp and other ophthalmic examinations, and the percentiles and growth curve of uncorrected visual acuity of children and adolescents in the relative safe refractive range were fitted by LMS method. Besides, the area under the ROC curve and the sensitivity and specificity of different cut-off values were analyzed. Results: The uncorrected visual acuity was skewed, with a median of 4.8. There were 4 675 individuals with safe refraction, the median of uncorrected visual acuity in which was 4.9. The LMS curve showed that the uncorrected visual acuity increased with age in the lower age group, and gradually stabilized to the best level at the age of 6-10. P 50 was 4.8 in 3-4 years old, 4.9 in 5-8 years old, 5.0 in 9 years old and above. The area under ROC curve of uncorrected visual acuity predicting refractive abnormality increased with age, with the lowest value of 0.55(95%CI=0.50-0.61) at 3 years old and the highest value of 0.95 (95%CI=0.94-0.96) at 12-18 years old. The Youden index was the highest for P25 at 3-6 years old, and the highest for P 10 at 7 years old and above. With the increase of the cut off value, the sensitivity increased and the specificity decreased. Conclusion The uncorrected visual acuity increases gradually with age, and reaches the best level after 6-10 years old. The screening effect of uncorrected visual acuity predicting refractive abnormality increased with age. It is suggested that the referral threshold of children and adolescents with abnormal uncorrected visual acuity should be set according to their ages, and P 25-P 75 can be selected according to the screening purposes.