Objective · To understand boys' pubertal timing in school in two urban districts of Chongqing and explore the relationship between pubertal timing and physical activity or sleeping time. Methods · Using a stratified random cluster sampling, 3403 boy students (10-18 year-old) were selected and completed the physical examination and questionnaire survey. 1282 participants experiencing first spermatorrhea were chosen as research objects. According to age of first spermatorrhea, the objects were divided into on-time group (964 cases) and later group (318 cases). Results · The composition of weekly high (χ2=11.488, P=0.009), medium (χ2=7.829, P=0.050) physical activity and daily sleeping time (χ2=17.803, P=0.000) in two groups were significantly different. Controlling covariates (age, height and weight), compared with boys in on-time group, later group boys were less likely to engage in 5-7 days (OR=0.596, 95% CI: 0.367-0.967) and 3-4 days (OR=0.590, 95% CI: 0.370-0.941) high physical activity every week, and 9-11 h (OR=0.207, 95% CI: 0.088-0.489) sleep every day. Conclusion · The age of first spermatorrhea in boys might be associated with the intensity of weekly physical activity and daily sleeping time.