Objective · To observe changes of exhaled nitric oxide (FeNO) level in patients with chronic obstructive pulmonary disease (COPD) before and after inhaled corticosteroid (ICS) therapy and to explore the correlation of FeNO level with inflammation and pulmonary function indexes. Methods · Seventy COPD patients at stable stage who underwent ICS therapy (the COPD group) were enrolled. Levels of peripheral blood eosinophil (Eos) and neutrophil (N), FeNO, PEF, FEV1 and FEV1/pred before and after treatment were measured. Fifty healthy volunteers who received physical examination at the same time served as controls (the control group). The relationship between these indexes and clinical efficacy and the correlation between FeNO level and inflammation or pulmonary function indexes were analyzed. Results · The COPD group had significantly higher FeNO, Eos, and N levels before treatment, significantly lower PEF, FEV1 and FEV1/pred after treatment (P<0.05), and remarkably better indexes after treatment (P<0.05) compared with the control group. Indexes of the effective group and the improved group were significantly better than that of the ineffective group after treatment. Results of correlation analysis showed that before treatment, the FeNO level was positively correlated with peripheral blood Eos and N levels (P<0.05) and negatively correlated with PEF, FEV1 and FEV1/pred (P<0.05). After treatment, the FeNO level was positively correlated with peripheral blood Eos and N levels (P<0.05) and the correlation of the FeNO level with PEF, FEV1 and FEV1/pred was not statistically significant (P>0.05). Conclusion · The FeNO level increased significantly in patients with COPD at stable stage and is a sensitive index of airway inflammation. Combined with lung function test, it’s useful for evaluating the efficacy of ICS and guiding treatment.