Background Although exposure to cigarette smoking and air pollution is common, the current prevalence of chronic obstructive pulmonary disease (COPD) is unknown in the Chinese adult population. We conducted the China Pulmonary Health (CPH) study to assess the prevalence and risk factors of COPD in China. Methods The CPH study is a cross-sectional study in a nationally representative sample of adults aged 20 years or older from ten provinces, autonomous regions, and municipalities in mainland China. All participants underwent a post-bronchodilator pulmonary function test. COPD was diagnosed according to 2017 Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria. Findings Between June, 2012, and May, 2015, 57 779 individuals were invited to participate, of whom 50 991 (21 446 men and 29 545 women) had reliable post-bronchodilator results and were included in the final analysis. The overall prevalence of spirometry-defined COPD was 8 . 6% (95% CI 7 . 5-9 . 9), accounting for 99 . 9 (95% CI 76 . 3-135 . 7) million people with COPD in China. Prevalence was higher in men (11 . 9%, 95% CI 10 . 2-13 . 8) than in women (5 . 4%, 4 . 6-6 . 2; p< 0 . 0001 for sex difference) and in people aged 40 years or older (13 . 7%, 12 . 1-15 . 5) than in those aged 20-39 years (2 . 1%, 1 . 4-3 . 2; p< 0 . 0001 for age difference). Only 12 . 0% (95% CI 8 . 1-17 . 4) of people with COPD reported a previous pulmonary function test. Risk factors for COPD included smoking exposure of 20 pack-years or more (odds ratio [OR] 1 . 95, 95% CI 1 . 53-2 . 47), exposure to annual mean particulate matter with a diameter less than 2 . 5 mu m of 50-74 mu g/m(3) (1 . 85, 1 . 23-2 . 77) or 75 mu g/m(3) or higher (2 . 00, 1 . 36-2 . 92), underweight (body-mass index <18 . 5 kg/m(2); 1 . 43, 1 . 03-1 . 97), sometimes childhood chronic cough (1 . 48, 1 . 14-1 . 93) or frequent cough (2 . 57, 2 . 01-3 . 29), and parental history of respiratory diseases (1 . 40, 1 . 23-1 . 60). A lower risk of COPD was associated with middle or high school education (OR 0 . 76, 95% CI 0 . 64-0 . 90) and college or higher education (0 . 47, 0 . 33-0 . 66). Interpretation Spirometry-defined COPD is highly prevalent in the Chinese adult population. Cigarette smoking, ambient air pollution, underweight, childhood chronic cough, parental history of respiratory diseases, and low education are major risk factors for COPD. Prevention and early detection of COPD using spirometry should be a public health priority in China to reduce COPD-related morbidity and mortality.