Abstract： Objective Serum of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinases-1 (TIMP-1) levels moderate and severe acute exacerbations of chronic obstructive pulmonary disease (AECOPD) patients before and after treatment were tested using ELISA to observe the effect of montelukast modiumr on serum MMP-9 and TIMP-1 levels.Methods Sixty-three cases mild moderate and severe AECOPD were selected that were randomly divided into 30 cases as treatment group and 33 cases as control group.The treatment group were given conventional therapy plus montelukast sodium (10 mg oral treatment once-daily for 7-14 days).The control group were given conventional therapy for 7-14 days.Serum of MMP-9 and TIMP-1 levels in moderate and severe AECOPD patients before and after treatment were tested using ELISA and compared with its changes.Results ①Before the treatment,the comparison of MMP-9 serum level between the treatment group and control group has no significant difference (P ＞0.05).While the serum level in treatment group [(22.02 ± 6.34)μg/L] is higher than the control group after the treatment [(26.31±8.23) μg/L](P ＜0.05).The serum level in the treatment group [(27.59 ± 7.71) μg/L] and control group [(27.74 ± 7.96) μg/L] is respectively higher than group after the treatment [(22.02 ± 6.34) μg/L],[(26.31 ± 8.23) μg/L] (P ＜0.05).②Serum level of TIMP-1 before the treatment has no significant difference between the treatment group and control group(P ＜ 0.05).Though the serum level after the treatment is different between these two groups [(22.23±5.52) μg/L],[(17.23±8.23) pg/L,respectively](P ＜0.05).The serum level in the treatment group [(16.34±1.45) μtg/L] and control group [(16.20±2.03) μg/L] is respectively higher than group after the treatment [(22.23 ± 5.52) μg/L,(17.23 ± 2.45) pg/L,respectively (P ＜ 0.05).Conclusions Montelukast sodiumr do have an effect on serum level of MMP-9 and TIMP-1 in AECOPD,which seems that montelukast sodiumr may alleviate the inflammation in air flue and delay the airway remodeling.