Abstract: Objective To investigate the susceptibility factors of a sthma among children in suburban region of Beijing and to provide reference to intervene asthma.Methods A cross-sectional survey was conducted among the parents of 27445 pupils of grade1 to grade 5 selected with random cluster sampling.Then a case-control study was carried out among 370 cases and 868 controls selected from the study population.The data on influence factors of a sthma were obtained with a questionnaire to their parents.Results The frequency of low birth weight,non-full-term birth,breast-feeding more than 6 months,family history of asthma,family history of a llergy,having allergy,passive smoking,and noventilation while cooking with coal at home was 8.4%,10.0%,69.7%,21.4%,26.2%,34.3%,77.0%,and 26.8% in case group and 4.2%, 6.0%,75.7%,8.3%,17.7%,11.7%,70.6%,and 19.8% in the control group,respectively,with significant differences between the two groups(P < 0.05 for all).Multivariate logistic regression showed that low birth weight,family history of asthma or allergy,having allergy,and no ventilation while cooking with coal were risk factors of childhood a sthma in suburban region of Beijing;breast-feeding more than 6 months was a protective factor.Conclusion The children with low birth weight,family history of asthma or allergy,having allergy,no ventilation while cooking with coalat hometend to have a higher prevalence of asthma,whereas breast-feeding more than 6 months decreases the risk of asthma.