Abstract: OBJECTIVE To explore the characteristics of potentially pathogenic microorganisms (PPMs) in respiratory tract in stable COPD patients and the associations between PPMs and airway inflammation and COPD exacerbations, so as to provide references for clinical treatment. METHODS A total of 185 patients with stable COPD meeting the criteria from Jan.2014 to Dec.2014 were selected as research subjects. Qualified sputum specimens were obtained by expectoration or induction method. Sputum white blood cells were counted and bacteria were cultured. Subsequently followed up were conducted with a follow-up interval for 3 months and for 3 times. Sputum white blood cells were counted and bacterial were cultured at each visit. RESULTS The positive rate of PPMs was 37.3% (69/185), and the most commonly detected PPM was Haemophilus influenzae (HI), with a positive rate of 17.8% (33/185). A total of 163 cases of patients completed sputum examination at 4 visits. PPMs negative rate, once PPMs positive rate, twice PPMs positive rate and 3/4 times PPMs positive rate were 45.4% (74/163), 23.3% (38/163), 18.4% (30/163) and 12.9% (21/163), respectively. CONCLUSION Stable COPD patients have a high PPMs positive rate in respiratory tract, especially Haemophilus influenzae which shows persistent and is closely related to respiratory tract inflammation.