Objective: The study aims to analyze the prevalence and associated factors of myopia among 4 to 9 grade students in Guangdong Province in 2022, so as to provide a scientific basis for targeted intervention measures for myopia in children and adolescents. Methods: From September to October 2022, stratified cluster random sampling was used to select 29 095 of 4 to 9 grade students from Guangzhou, Jiangmen, and Meizhou in Guangdong Province for myopia screening and questionnaire surveys. The Chisquare test was applied to compare the differences between groups, and multivariable Logistic stepwise regression analysis was used to analyze factors associated with myopia. Results: The myopia detection rate of 4 to 9 grade students was 61.7%, with detection rates of 51.5% for 4 to 6 grade primary school students and 71.95% for 7 to 9 grade junior high school students. Multivariable Logistic regression analysis showed that higher myopia rates were detected among girls (OR=1.39, 95%CI=1.30-1.49), students with one (OR=1.82, 95%CI=1.69-1.96) or both parents having myopia (OR=2.86, 95%CI=2.56-3.18), and indoor sedentary time >6 h(OR=1.28, 95%CI=1.17-1.39) in the 4 to 6 grade. Lower myopia rates were detected in the county (OR=0.92, 95%CI=0.86-0.99) and outdoors at recess activities (OR=0.88, 95%CI=0.81-0.95). Meanwhile, higher myopia rates were detected among girls (OR=1.84, 95%CI=1.69-1.99), students with one (OR=1.87, 95%CI=1.71-2.04) or both parents having myopia (OR=3.03, 95%CI=2.63-3.50), and indoor sedentary time >6 h/d (OR=1.11, 95%CI=1.01-1.23) in the 7 to 9 grade. Lower myopia rates were detected in the county (OR=0.74, 95%CI=0.68-0.80), outdoors at recess activities (OR=0.83, 95%CI=0.76-0.91), and outdoor activity time ≥2 h/d(OR=0.87, 95%CI=0.80-0.95)(P<0.05). Conclusions The detection rate of myopia among 4 to 9 grade students in Guangdong Province is relatively high. Place of recess activities, daily outdoor activity and indoor sedentary duration are associated with myopia. Therefore, targeted intervention measures should be adopted, such as appropriately increasing outdoor activity to reduce the occurrence of myopia among primary and middle school students.