Objective To explore the role of matrix metalloproteinase 9(MMP-9)and tissue inhibitor of metalloproteinase-1(TIMP-1)in patients with acute exacerbation of severe chronic obstructive pulmonary diseases (AECOPD)treated with glucocorticoids.Methods The serum levels of MMP-9 and TIMP-1 were measured by ELISA in 41 patients with AECOPD before and after treatment with glucocorticoids and in 40 patients with regular methods(control group).Results ①After treatment with glucocorticoids,the serum levels of MMP-9(189.25±52.38)μg/L、TIMP-1(198.38±43.45)μg/L,ratio of MMP-9/TIMP-1(0.92±0.37)were decreased significantly than before((246.10±68.64)μg/L,(217.63±62.34)μg/L,(1.09±0.23))(P<0.01,P<0.05,P<0.05);but there were no differences(P>0.05)in regular methods(control group);② After treatment with glucoeorticoids, FEV_1、FEV_1%((0.83±0.35)L,(46±17)%)were impmved than before((0.72±0.48)L,(34±15)%)(P<0.05).Conclusions After treatment with glucocorticoids,the serum levels of MMP-9、TIMP-1、ratio of MMP-9/TIMP-1 from patients with COPD were decreased significandy,and FEV_1、FEV_1%were improved significant;Glucocorticoids can alleviate severs AECOPD to some degrees,which might be related to improving the imbalance of MMP-9/TIMP-1.