Objective To investigate the clinical significance of noninvasive detection of end-tidal carbon dioxide partial pressure (PetCO2) in the management of children with acute asthma, and to evaluate the association between PetCO2 and artery blood gas carbon dioxide partial pressure ( PaCO2 ). Methods This was a prospective,double blinded study of children aged 5 ～ 14 years old treated for acute asthma in a pediatric emergency department. PetCO2 and PaCO2 measurements were taken before therapy and after each nebulization treatment ( maximum of three). Various clinical parametesr were recorded. Patients with PaCO2 and PetCO2 measurements within 8 minutes of each other were eligible for inclusion. Patients with cardiac disease,chronic pulmonary disease, poor tissue perfusion, or metabolic abnormalities were excluded. Results Sixty five children were enrolled. The initial PetCO2 value was (34. 8 ±8. 6) mm Hg (95% confidence interval =34. 0 to 36. 1). The PetCO2 value of post-treatment was (33.2 ±8.2) mm Hg (95% confidence interval =32. 5 to 34. 4) ,which was decreased significantly than that before treatment(P ＜ 0. 01 ). Fifty seven PetCO2-PaCO2 paired values were available from 57 patients. The values of PetCO2 and PaCO2 were ( 34. 8 ±7. 6) mm Hg and (40. 6 ± 8. 3 ) mm Hg, respectively. PetCO2 and PaCO2 values were highly positively correlated ( r = 0. 92,P ＜ 0. 000 1 ). Conclusion Noninvasive bedside measurement of PetCO2 in children with acute asthma in emergency department is feasible. Continuous PetCO2 monitoring can provide a reliable assessment of pulmonary status. PetCO2 can serve as an important adjunct index in the clinical management of pediatric patients with acute asthma.