Objective: To investigate the prevalence of chronic obstructive pulmonary diseases (COPD) in Tongxiang, Zhejiang province, and analyze the interaction between smoking and indoor air pollution on COPD. Methods: Townships of Chongfu, Zhouquan, Gaoqiao, Shimen, Wuzhen were randomly selected from Tongxiang. All the local people aged 30-79 years were asked to receive questionnaire survey, physical examination and pulmonary function testing. FEV1max/FVC max≤0.7 was the criterion of COPD diagnosis. Logistic regression model was used to analyze the relationship between smoking/indoor air pollution and COPD, multiplied interaction between smoking and indoor air pollution was evaluated, Excel table prepared by Andersson et al. was used to calculate the adding interaction. Results: The overall prevalence of COPD was 6.6%, and adjusted for age, educational level, occupation, marriage, income level, BMI, waist-to-hip and other factors, multivariate logistic regression analysis showed that males who had quit smoking, started smoking at age of <25 years had a high risk of COPD; females who smoked every day <15 g, inhaled smoke into mouth or throat had high risk of COPD. Interaction analysis showed that using fuel of firewood/charcoal/coal, briquettes for cooking and regular smoking had multiplied interaction on COPD. Use no chimney or exhaust system in cooking and regular smoking had adding interaction in females. Conclusion: The prevalence of COPD in Tongxiang was close to the national average level. Female smokers had higher risk for COPD than male smokers. Improving kitchen ventilation, using natural gas or fuel gas for cooking and active tobacco control would facilitate the prevention of COPD.