| Objective To investigate the expression and clinical significance of microRNA-223 (miRNA-223) in serum exosomes of patients with chronic obstructive pulmonary disease (COPD).Methods A total of 113 stable COPD patients treated in the Departmentof Respiratory, Jining First People′s Hospital from March 2019 to June 2021 were selected as observation objects (COPD group), andaccording to lung function, COPD patients were assigned into mild group with 40 cases, moderate group with 31 cases, severe groupwith 25 cases, and extremely severe group with 17 cases. In addition, 100 healthy medical examiners who were examined in this hospital during the same period were selected as the control group. The serum exosomes of each research object were extracted and identified; the serum exosomal miRNA-223 level, serum inflammatory factors TNF-α, IL-6, C-reactive protein (CRP) levels, and lung function indicators forced expiratory volume in first second (FEV1) and the percentage of FEV1 to the estimated value (FEV1%pred), thepercentage of FEV1 to vital capacity (FVC) (FEV1/FVC) were tested; the correlation between serum exosomal miRNA-223 and TNF-α, IL-6, CRP, FEV1% pred, FEV1, FEV1/FVC in COPD patients was analyzed with Pearson. Results Lung function indexes FEV1%pred (62.05±11.38 vs. 101.87±12.45), FEV1 [(1.77±0.62) L vs. (2.83±0.44) L], FEV1/FVC [(64.01±11.52)% vs. (86.47± 8.08)%] in COPD group were significantly lower than those in control group (P<0.05); the results of electron microscopy showed that the serum exosomes were round or elliptical vesicle-like structures, with a diameter of about 100 nm; Western blot results showed thatthe exosomes of the control group and COPD group both expressed specific proteins CD63, CD9 and TSG101, indicating that the serumexosomes were successfully extracted and could be used for subsequent experiments. The level of serum exosomes miRNA-223 and serum levels of TNF-α, IL-6, and CRP in the COPD group were significantly higher than those in the control group (P<0.05); the expression level of serum exosomal miRNA-223 in the mild, moderate, severe, and extremely severe groups increased sequentially, and thedifference between the two groups was statistically significant (P<0.05). Serum levels of TNF-α, IL-6 and CRP in patients with severeand very severe COPD were significantly higher than those in patients with mild and moderate COPD (P<0.05). There was no significant difference in serum TNF-α, IL-6 and CRP levels between mild and moderate, severe and very severe COPD patients (P>0.05). Correlation analysis showed that serum exosomal miRNA-223 level in COPD patients was positively correlated with TNF-α, IL-6, and CRP levels, and negatively correlated with FEV1% pred, FEV1, FEV1/FVC (both P<0.05).Conclusion The expression level of miRNA223 in the serum exosomes of COPD patients is elevated, and it is related to the severity of the patient′s disease, and may be used as apotential marker for judging the severity of COPD.