Objective To investigate the significance of serum matrix metalloproteinase⁃9（MMP⁃9）andmatrix metalloproteinase tissue inhibitor 1（TIMP⁃1） in the development of respiratory syncytial virus（RSV）bronchiolitis to asthma. Methods The serum MMP⁃9 and TIMP⁃1 of RSV bronchiolitis children（RSV group）andhealth control were determined，and the RSV group were divided into non⁃asthmatic subgroup and asthma subgroupaccording to the follow⁃up results. ROC curve and logistic regression were used to analyze the performance ofMMP⁃9，TIMP⁃1 and MMP9/TIMP⁃1 in the diagnosis of RSV bronchiolitis and its progression to asthma. Results Compared with those in the control group，MMP⁃9，TIMP⁃1 and MMP9/TIMP⁃1 in the RSV group were significantlyincreased（P < 0.05）. The area under the curve（AUC）of MMP⁃9，TIMP⁃1 and MMP9/TIMP⁃1 for the diagnosisof RSV bronchiolitis was 0.942，0.579，and 0.827，respectively. Compared with those in non⁃asthmatic group，MMP⁃9 and MMP9/TIMP⁃1 in asthma group were significantly increased（P < 0.05）. MMP⁃9 and MMP⁃9/TIMP⁃1were independent risk factors in the development of RSV bronchiolitis to asthma（P < 0.05）. Conclusion SerumMMP⁃9 and TIMP⁃1 have certain significance in RSV bronchiolitis and its progression to asthma.