Abstract: 　Objective　To investigate the clinical significance of changes of the airway size and its function indicators in asthmatic children using dilation test. Methods　From October 2012 to April 2014, 51 children with initial attack of asthma were selected. Master Screen spirometer were used before and after nebulized albuterol sulfate pulmonary function testing; forced vital capacity (FVC), peak expiratory flow (PEF), one second forced vital capacity (FEV1), 1 second ratio (FEV1 / FVC), peak expiratory flow in the middle (MMEF), forced expiratory flow (FEF)25, FEF50, FEF75 changes were compared. Results　The average age of 51 children included in this study was (7.30 ± 2.33) years. The positive rate of dilation test was 58.8% in children with asthma onset, and increased with severity of the disease. The size of the airway absolute value of each index, percentage predicted after the test increased significantly than that before the test (P<0.05); FEV1 positive rate was 58.8%, and MMEF positive rate was 70.6%, which showed no statistically significant difference (P>0.05). Conclusions　Asthmatic children with baseline FEV1>70% can be given relaxation experiments, and indicators of large and small airways could be combined to determine the airway reversibility, which can be a better reflection of the severity of asthma.