Inclusion Criteria:  Clinical diagnosis of COPD age ≧ 40  Exclusion Criteria:  Presence of other chronic respiratory diseases other than COPD, such as asthma, bronchiectasis, interstitial lung disease, etc. History of chest and lung surgery. History of malignancy. Autoimmune disease. Long-term oral glucocorticoids, immunosuppressants and inhaled glucocorticoids. Mental abnormalities, cognitive impairment, inability to cooperate with pulmonary function and other tests. Acute stage of infection, such as lung infection, urinary tract infection and gastrointestinal tract infection, etc.