Objective To investigate the clinical characteristics and risk factors of asthma-chronic obstructive pulmonary disease overlap syndrome (ACOS), and to provide reference for clinic. Methods 20 patients with ACOS and 40 patients with chronic obstructive pulmonary disease (COPD) admitted to Suzhou Wuzhong People’s Hospital from January 2019 to December 2022 were selected for retrospective analysis. They were included in ACOS group and COPD group respectively. Clinical data were collected and analyzed. The general data [age, gender, BMI, basic complications (hypertension, diabetes), smoking history, drinking history], clinical characteristics [initial symptoms (polypnea, cough and sputum), physical signs (simple dry rales, simple wet rales, dry and wet rales, no rales), pathogenesis (bacterial pneumonia, viral pneumonia, bronchiectasis with infection), lung function indexes [forced expiratory volume for 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC] and laboratory indexes [C-reactive protein (CRP), tumor necrosis factor-α (TNF-α)] of the two groups were compared. Multiple Logistic regression analysis was used to identify the independent risk factors of ACOS. Results There were no significant differences in gender, basic complications, smoking history, drinking history, simple wet rales, no rales, pathogenesis ratio between the two groups, and there were no significant differences in age and BMI between the two groups (P> 0.05). The proportion of cough and sputum in the initial symptom in ACOS group was higher than that in COPD group, the proportion of polypnea was lower than that in COPD group, the proportion of dry and wet rales in physical signs was higher than that in COPD group, and the proportion of simple wheezing was lower than that in COPD group (P<0.05). CRP and TNF-α levels in ACOS group were higher than those in COPD group, while FVC, FEV1 and FEV1/FVC were lower than those in COPD group (P<0.05). Multivariate Logistic analysis showed that physical signs and initial symptoms were not independent risk factors for ACOS (P>0.05), but low FEV1, FVC, FEV1/FVC and high CRP and TNF-α were independent risk factors for ACOS (P<0.05). Conclusion The initial symptoms of ACOS patients are mostly cough and sputum, and the signs are mostly dry and wet rales. Low FEV1, FVC, FEV1/FVC and high CRP, TNF-α are independent risk factors for ACOS.