A total of 84 cases of pediatric patients with bronchiolitis were selected as bronchiolitis group， and they were divided into mild bronchiolitis group （n=46） and moderate-severe bronchiolitis group （n=38） according to the severity of the disease.Another 20 healthy infants who underwent physical examination at the same time were selected as healthy control group.The levels of serum TGF-β1 and the ridal breathing pulmonary function indexes of the pediatric patients at acute and convalescent phases and the subjects in healthy control group were detected， and Pearson correlation analysis was used to analyze the correlations between the serum level of TGF-β1_{and the tidal breathing pulmonary function indexes.}

The serum levels of TGF-β1 of the pediatric patients in mild bronchitis group and moderate-severe bronchiolitis group at acute phase were significantly higher than those in healthy control group （P<0.01）. Compared with mild bronchitis group， the serum TGF-β1 level of the pediatric patients in moderate -severe bronchiolitis group at acute stage was significantly increased （P<0.01）. Compared with acute stage， the serum TGF-β1_{levels of the pediatric patients in mild and moderate-severe bronchiolitis groups at convalescence stage were significantly decreased （P<0.01）. The TPTEF/TE and VPEF/VE of the pediatric patients in mild and moderate- severe bronchiolitis groups were significantly lower than those in healthy control group （P<0.05）. Compared with mild bronchiolitis group， the TPTEF/TE and VPEF/VE of the pediatric patients in moderate-severe bronchiolitis group were significantly decreased （P<0.05）. There was no significant difference in the tidal volume per kilogram of body weight among the subjects in three groups （P>0.05）.The serum level of TGF-β1 of the bronchiolitis pediatric patients was negatively correlated with TPTEF/TE and VPEF/VE （r=－0.552， P<0.01； r=－0.517，P<0.01）.}

The serum level of TGF-β1 in the bronchiolitis pediatric patients can indirectly reflect the degree of airway obstruction， which can be used as a reference indicator for the condition judgment of bronchiolitis and the prognosis evaluation of lung function.