Objective: To explore the relationship between paternal smoking and risk of childhood obesity , and to provide theoretical support for the identification and intervention of risk factors of obesity among children and adolescents. Methods: Physical examination and questionnaire survey was conducted among 38 228 students from 7 provinces in China. Log-binomial regression model was used to estimate the relationship between passive smoking and childhood obesity. Results: The students were divided into non-smoking goroup and smoking group auording to whether their fathers smoked or not, the former included 19 096 students(50.0%), and the latter included 19 132 students(50.0%). The obesity rate of the no-smoking group was 10.2%, the obesity rate from smoking group was 12.7%, the differences were of statistical significace (χ2=58.42, P<0.01). Univariate analysis showed that the risk for obesity in smoking group was 1.24 times higher than those in non-smoking group (95%CI=1.18-1.32, P<0.05). Adjusting regression indicated that the risk for obesity in smoking group was 1.28. times higher than non-smoking group (95%CI=1.21-1.35, P<0.01). Conclusion Paternal smoking increases the risk of obesity in children and adolescents. Parents should avoid smoking and other unhealthy lifestyle, so as to effectively control the incidence of obesity in children and adolescents.