Objective : To examine the association between acute exposure to traffic-related air pollutants (TRAP) NOX and NO2 and outpatient visits of pediatric respiratory diseases. Methods : Data regarding outpatient visits to Department of Respiratory Diseases of Beijing Children's Hospital from 2015 to 2020 were collected, and the concentrations of nitrogen oxides (NOX), nitrogen dioxide (NO2) and other TRAP were collected from the surveillance sites assigned by the Peking University Health Science Center. A time-stratified case-crossover design was employed, and a conditional logistic regression model was created to examine the association between NOX and NO2 acute exposure and outpatient visits of pediatric respiratory diseases. Results : The daily mean outpatient visits of pediatric respiratory diseases were 571 (interquartile range, 554) person-times among children at ages of 0 to 14 years in Beijing Children's Hospital from 2015 to 2020, and the daily mean outpatient visits for upper respiratory tract infections (URI), bronchitis, and pneumonia were 265 (interquartile range, 282), 143 (interquartile range, 178) and 128 (interquartile range, 120) person-times, respectively. The daily mean concentrations of atmospheric NOX and NO2 were 67.8 (interquartile range, 50.7) and 49.3 (interquartile range, 30.7) μg/m3, respectively. Conditional logistic regression analysis showed the largest lagged effect of NOX and NO2 on pediatric respiratory diseases at cumulative lags of 0 to 7 days. An increase in NOX concentrations by an interquartile range resulted in the excess risks of URI, bronchitis and pneumonia by 6.87% (95%CI: 6.37%-7.38%), 7.25% (95%CI: 6.51%-7.99%), and 5.51% (95%CI: 4.69%-6.33%), and an increase in NO2 concentrations by an interquartile range resulted in excess risks of URI, bronchitis and pneumonia by 5.71% (95%CI: 5.12%-6.31%), 5.32% (95%CI: 4.51%-6.14%), and 4.83% (95%CI: 3.91%-5.75%), respectively. NOX and NO2 presented a more remarkable effect on outpatient visits of pediatric respiratory diseases among children at ages of over 5 years. Conclusion NOx and NO2 acute exposure may increase the outpatient visits of pediatric respiratory diseases.