Occupational exposure to inorganic dusts such as coal and crystalline silica has been identified as a chronic obstructive pulmonary disease (COPD) risk factor. This risk factor causes abnormal lung inflammation and protease-antiprotease imbalance. Abnormal inflammatory response of the lung induces parenchymal tissue destruction and leads to progressive airflow limitation that is characteristics of COPD. The aim of this study was to determine the relationship of proteases such as neutrophil elastase (NE) and matrix metalloproteinase (MMP)-9 and antiproteases such as alpha-1 antitrypsin (AAT) and tissue inhibitors of metalloproteinase (TIMP)-1 with lung function. The study population contained 223 male retired coal miners. We performed lung function test and analyzed MMP-9, AAT, TIMP-1 in serum and NE in plasma by enzyme-linked immonosorbent assay (ELISA). NE, AAT, and The levels of TIMP-1 in workers, who had %FEV₁ < 80%, were higher than those of workers who had %FEV₁ ≥ 80%. The levels of AAT and TIMP-1 in workers with airflow limitation were higher than those of workers with normal. %FEV₁ showed significant negative correlation with AAT, TIMP-1, and NE. %FEV₁/FVC showed significant negative correlation with NE. From the results of stepwise multiple regression analysis about %FEV₁ and %FEV₁/FVC, significant independents were NE and AAT in %FEV₁, and NE in %FEV₁/FVC. There were significant relationships between airflow limitation and protease and antiprotease concentration. The levels of proteases and antiproteases, however, may be affected by the biological and inflammatory responses. It is necessary to evaluate specimens more reflected the effects of proteases and antiproteases imbalance in the lung such as lung tissue and bronchoalveolar lavage fluid.