Objective:To analyze the level of fractional exhaled nitric oxide (FeNO) and its influencing factors in patients with chronic obstructive pulmonary disease (COPD).Methods:678 patients with stable COPD(COPD group), 281 patients with asthma-COPD overlap(COPD with asthma group) and 120 healthy nonsmoker controls (healthy control group) were recruited from the outpatient clinics of Xiangya Second Hospital of Central South University and the 1st People′s Hospital of Huaihua from November 2016 to December 2021. The gender, smoking status, age, height, weight, body mass index (BMI), FEV 1% predicted value (FEV 1% pred), forced expiratory volume in 1 second/forced vital capacity (FEV 1/FVC%), and FeNO value among the three groups were compared. Multiple linear regression analysis was performed to analyze the influencing factors of FeNO levels in COPD patients. Results:There was no significant difference in gender, smoking status, age, height, weight and BMI among the three groups (all P>0.05). The FEV 1% and FEV 1/FVC% in COPD group were lower than those in healthy group and COPD combined with asthma group (all P<0.05). The FeNO in COPD group was lower than that in COPD and asthma group, but higher than that in healthy group (all P<0.05). Univariate analysis showed that FeNO levels in COPD patients were associated with height, BMI, Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) classification, and Chronic Obstructive Pulmonary Disease Assessment Test (CAT) score (all P<0.05). Multiple linear regression analysis showed that FeNO level was positively correlated with height ( β=0.094, P=0.014), CAT score ( β=0.129, P=0.001), and negatively correlated with BMI ( β=-0.093, P=0.016). There was no significant correlation between GOLD grading and FeNO level ( P>0.05). Conclusions:The level of FeNO in patients with COPD is higher than that in healthy subjects, which is related to height, BMI and CAT.