The associations of long-term exposure to various constituents of fine particulate matter (≤2.5 μm in aerodynamic diameter, PM_2.5) air pollution with lung function were not clearly elucidated in developing countries. The aim was to evaluate the associations of long-term exposure to main constituents of PM_2.5 with lung function in China. This is a nationwide, cross-sectional analysis among 50,991 study participants from the China Pulmonary Health study. Multivariable linear regression models were used to obtain differences of forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), FEV₁/FVC, peak expiratory flow (PEF), and forced expiratory flow at 25–75% of exhaled FVC (FEF_25-75%) associated with an interquartile range (IQR) change of PM_2.5 or its constituents. Residential annual PM_2.5 levels varied from 26 μg/m³ to 92 μg/m³ (average: 53 μg/m³). An IQR increase of PM_2.5 concentrations was associated with lower FEV₁ (19.82 mL, 95% CI: 11.30–28.33), FVC (17.45 mL, 95% CI: 7.16–27.74), PEF (86.64 mL/s, 95% CI: 59.77–113.52), and FEF_25-75% (31.93 mL/s, 95% CI: 16.64–47.22). Black carbon, organic matter, ammonium, sulfate, and nitrate were negatively associated with most lung function indicators, with organic matter and nitrate showing consistently larger magnitude of associations than PM_2.5 mass. This large-scale study provides first-hand epidemiological evidence that long-term exposure to ambient PM_2.5 and some constituents, especially organic matter and nitrate, were associated with lower large- and small- airway function.