Abstract: Air pollution is an important factor affecting children's lung function. At present, the evidence of correlation research mostly comes from developed countries, and the research mainly focuses on the impact of fine particles. This study aims to investigate the effects of short-term exposure to air pollutants (PM_2.5, O₃) on pulmonary function of school-age children in China. From 2014 to 2015, 1081 children in grades 3—5 in 7 cities of Jiangsu province are selected for repeated measurements and questionnaire surveys of pulmonary ventilation function (FVC). A linear mixed effects model is used to analyze the relationship between air pollutants and lung function. The results of the study show that exposures to PM_2.5 and O₃ obviously have acute effects on lung function on the same day and also on the subsequent days with accumulative effects. For every 10 μg/m³ increase in PM_2.5 and O₃ concentrations on a day, FVC decreases by 8.8 (95%CI: 4.0—13.7) mL and 21.1 (95%CI: 13.8—28.4) mL, respectively. The concentration of PM_2.5 with a cumulative lag of 5 d has the greatest impact on FVC, and the concentration of O₃ with a cumulative lag of 7 d has the greatest impact on FVC. PM_2.5 has a greater effect on pulmonary ventilation in boys and children with allergies. These results indicate that short-term exposure to PM_2.5 and O₃ affects children's lung function, and it is of great significance to take appropriate personal protective measures.