Abstract: Objective To understand the correlation between sleep chronotype and myopia among junior high school students, and to provide scientific basis for myopia intervention. Methods This study was conducted as a cross-sectional survey using stratified cluster sampling. Four junior high schools were selected as the research sites. Two methods were used to assess chronotype, including sleep-wake pattern derived from sleep duration calculations and sleep chronotype evaluated by the Morningness-Eveningness Questionnaire-5 items (MEQ-5). Myopia status of students was determined through distant visual acuity examination combined with non-cycloplegic computerized refraction. SPSS 27.0 was used for x² testing and multivariate logistic regression analysis. Results A total of 801 junior high school students were enrolled in this survey, with a screening myopia rate of 81.77%. Univariate analysis showed that sleep chronotypes assessed by both sleep-wake pattern (χ²=4.536, P=0.033) and MEQ classification (χ²=12.748, P=0.013) were statistically correlated with myopia. After adjusting for grade, maternal age at birth, parental myopia, weekend outdoor activities, and sleep duration, multivariate analysis indicated that both higher grade (e.g., grade 9: OR=3.63, 95% CI=1.92-6.87) and myopia in both parents(OR=2.73, 95% CI=1.23-6.06) were associated with a higher risk of myopia. In contrast, older maternal age at birth (OR=0.64, 95% CI=0.49-0.85) and more frequent weekend outdoor activities (e.g., ≥5 times/week: OR=0.16, 95% CI=0.04-0.71) were associated with a lower risk of myopia. The association between MEQ chronotype and myopia was not statistically significant after multivariate adjustment (P=0.124). However, compared with “absolute evening type”, a decreasing trend in myopia risk was observed from “moderate evening type” (OR=3.22) to “absolute morning type” (OR=0.57). Conclusion Myopia in junior high school students is positively correlated with higher grade level and parental myopia, and negatively correlated with maternal age at birth and frequency of weekend outdoor activities. A tendency towards evening chronotype may be related to a higher risk of myopia, but this association requires further study.