Objective: To explore the association between parental myopia and extracurricular activities before school age with myopia among lower grade students, so as to provide evidence for myopia prevention on low grade students. Methods: From November 2020 to June 2022, a total of 8 368 students of grade 1-3 were selected from Beijing, Liaoning, Zhejiang, Henan, Chongqing, Shaanxi Province by the stratified cluster random sampling and probability sampling methods, and were administered with a questionnaire survey and eye examinations. Multivariate Logistic regression was used to analyze the association between parental myopia and extracurricular activities before school age with myopia among lower grade students. Results: The prevalence of myopia in grade 1-3 was 23.7% in 6 provinces in China. Students who in central area, grade 3, boarding at school, doing homework/reading/writing time ≥1 h/d after school, extracurricular activities ≥1 h in the past week, extracurricular activities before school age, parental myopia, poor reading and writing posture, sleeping time <10 h/d, less exercise time because of homework or extracurricular activities, having annual vision examination had a higher myopia detection rate, with statistically significant differences ( χ 2=36.41, 487.72, 15.97, 21.35, 43.95, 15.33, 54.04, 6.67, 3.88, 20.02, 20.06, P <0.05). After adjusted for the confounding factors, there was a significant interaction between parental myopia and extracurricular activities before school age with myopia ( P interaction <0.01). After adjusting for confounding factors, Logistic regression analysis showed that those having extracurricular activities before school age had a higher risk of myopia ( OR=1.33, 95%CI =1.19-1.56), compared with those who did not. Compared with children without nearsighted parents, children with nearsighted parents had higher prevalence of myopia ( OR=1.64, 95%CI = 1.45- 1.84) ( P <0.05); and the values of indicators ( RERI, API, Index S ) for interaction between parental myopia and extracurricular activities before school age were 0.35, 0.27, 1.37, respectively. Conclusion Both parental myopia and extracurricular activities before school age are associated with myopia among lower grade students, with interactive effects.