Background: The known risk factors of childhood OSAS include tonsillar and adenoidhypertrophy, obesity, craniofacial anomalies, neuromuscular disorders and African-American (AA) ancestry. Whether other factors such as allergic rhinitis (AR), premature, environmental tobacco smoking (ETS) are associated with OSAS are inconsistent in different studies. Our study enrolled children of a broad age range and included potential risk factors of OSAS derived from previous studies and our own experience. Our objective is to identify risk factors of OSAS in children in a clinical setting. Methods: Children between 2 and 15 years of age exhibiting snoring symptoms who visited the sleep center for polysomnography (PSG) were enrolled. All children completed a questionnaire, physical examination and PSG. The questionnaire included demographic data and information related to potential risk factors for sleep disorders. A physical examination included measurements of height, weight, neck circumference, waist and hip ratio, visual evaluation of the tonsils and the degree of adenoid obstruction. Children with obstructive apnea-hypopnea index (OAHI) ≥ 1 were defined as OSAS. Results: A total of 1578 children were enrolled and1009 children exhibited OSAS. Univariate analyses showed that snoring occurring for ≥ 3 months, male gender, preterm birth, breastfeeding, obesity, neck circumference ≥ 30 cm, waist/hip ratio ≥ 0.95, tonsillar hypertrophy, and adenoid hypertrophy were associated with OSAS. The proportion of low educational level was higher in parents who breastfed their babies than those who didn't. Multivariate analysis showed that snoring for ≥ 3 months, male gender, obesity, breastfeeding, tonsillar hypertrophy, and adenoid hypertrophy were associated with OSAS. Confounders such as socioeconomic status, parental occupation, and health-related behaviors should be explored further to investigate the relationship between breastfeeding and OSAS. Conclusion: The independent risk factors for OSAS in children included snoring ≥ 3 months, male gender, obesity, breastfeeding, tonsillar and adenoid hypertrophy. The study was registered on Clinical Trials government (NCT02447614). The name of the trial is "Follow-up Studies of Primary Snoring (PS) and Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS) in Chinese Children" and the URL is https://clinicaltrials.gov/. © 2020 The Author(s).