Objective To detect the levels of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in serum of chronic obstructive pulmonary disease (COPD)group and health control group,and analyzed the relationship between the levels and pulmonary function indicator or quantity of smoking.Methods Fifty six cases of serum samples with COPD,and twenty one cases of serum samples from health control were collected and analyzed.The COPD group was divided into two groups,one of acute exacerbation phase (AECOPD),and the other of stable phase (STCOPD).The levels of serum MMP-9 and TIMP-1 in aboved groups were measured by enzyme-linked immunosorbent assay (ELISA) method.Results 1.① The level of MMP-9 in AECOPD group is significantly higher than which in STCOPD group or health control group ( t =3.24,4.22,P ＜0.01).The level of MMP-9 in STCOPD group is significantly higher than which in health control group ( t =2.08,P ＜ 0.05).②The level of TIMP-1 in AECOPD group are significantly higher than which in STCOPD group or health control group ( t =2.02,3.65,P ＜ 0.05,0.01).There are significant difference between the level in STCOPD with the level in health group( t =2.11,P ＜0.05).③The ratio of MMP-9/TIMP-1 in AECOPD group are higher than which in STCOPD group or health control group ( t =2.51,2.11,P ＜0.05).There are no significant difference between the level in STCOPD with the level in health group ( t =-0.39,P ＞0.05).2.There is a negative correlatin between the levels of MMP-9 with FEV1 ％pred in AECOPD group (r =-0.37,P ＜0.05).There are positive correlation between the levels of MMP-9 with RV/TLC or the amount of smoking in AECOPD ( r =0.39,0.41,P ＜0.05).In STCOPD group,there are no correlation between the level of MMP-9 with FEV1 ％ pred or RV/TLC ( r =0.25,-0.26,P ＞0.05),and a positive correlation between the level and the amount of smoking ( r =0.50,P ＜0.05).3.In AECOPD group,there are a negative correlation between the level of TIMP-1 with FEV1 ％pred ( r =-0.51,P ＜0.01),and no correlation between the level with RV/ TLC or smoking ( r =0.36,0.28,P ＞0.05).In STCOPD group,there are no correlation between the level of TIMP-1 with FEV1 ％pred,RV/TLC or the level with smoking ( r =0.18,-0.15,0.17,P ＞0.05).4.There are no correlation between the ratio of MMP-9/TIMP-1 with FEV1 ％pred,RV/TLC or the level with smoking in AECOPD group and STCOPD group ( r =0.19,-0.02,0.06,0.17,-0.23,0.38,P ＞0.05).Conclusions 1.MMP-9,TIMP-1 and MMP-9/TIMP-1 play the important roles in the pathogenesis of COPD.2.MMP-9 and TIMP-1 can influence pulmonary function index of AECOPD patients directly.3.There is a significance correlation between the quantity of smoking and the levels of MMP-9,and which may be the important roles in the pathogenesis of COPD caused by smoking.