Background <p>There are no population-based school cohort studies reporting the incidence of early and precocious puberty in China. This study aims to determine the incidence of early and precocious puberty in China.</p> Methods <p>This prospective cohort study involved 8,025 children (4,341 boys and 3,684 girls) in China. Precocious puberty was defined as breast development stage II before 8 years or menarche before 10 years in girls, and testicular volume (TV) ≥ 4&#xa0;ml before 9 years in boys. Early puberty was defined as breast development stage III between 8 and 9.8 years or stage IV between 8 and 12.4 years in girls, and TV ≥ 4&#xa0;ml between 9 and 9.7 years or TV ≥ 12&#xa0;ml between 9 and 11.9 years in boys. Incidence was stratified by age, sex, BMI, and district.</p> Results <p>The adjusted incidence of precocious puberty was 1.7% (girls:2.9%; boys: 1.1%). Early puberty incidence was 3.9% (girls: 3.2%; boys: 4.5%). Urban boys had a higher incidence of early puberty (5.7%) compared to suburban boys (0.7%). Girls with overweight and obesity had higher incidences of early puberty (6.9% and 11.8%, respectively), with girls with obesity also showing a higher incidence of precocious puberty (4.6%).</p> Conclusion <p>The incidence of early and precocious puberty among children in these two Chinese cities was relatively high, particularly among girls.</p> Clinical trial number <p>Not applicable.</p>