Objective: To detect serum level of cysteine-rich angiogenic inducer 61 (Cyr61/CCN1) in patients with chronic obstructive pulmonary disease (COPD) and to analyze its correlation with severity of airflow restriction and body's immune function. Methods: A total of 136 COPD patients who were treated in Chongqing Yubei District People's Hospital from April 2016 to December 2019 were selected and divided into mild group, moderate group and severe+extremely severe group according to severity of airflow restriction, another 35 healthy checkups were selected as control group. Clinical data of study subjects in each group were compared. Serum CCN1 level was detected by ELISA, and its correlation with lung function and immune function was analyzed. Receiver operating characteristic (ROC) curve was used to evaluate predictive value of serum CCN1 level in patients with COPD to develop to severe/extremely severe airflow limitation. Results: Airflow restriction degree was increased with number of smoking years and smoking amount. Partial blood oxygen pressure (PaO2), eosinophil, forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC), forced expiratory volume in 1 second% pred( FEV1% pred), immunoglobulin A( IgA), IgM and IgG levels in COPD patients were all lower than control group, which were decreased with aggravation of airflow restriction. Partial carbon dioxide pressure (PaCO2), white blood cell count, percentage of neutrophils, mMRC score, CAT score, D-dimerization (D-D), procalcitonin (PCT), C-reactive protein (CRP), CCN1, myeloid dendritic cells( mDCs), plasmacytoid dendritic cells( pDCs) and mDCs/pDCs in COPD patients were higher than control group, which were increased with aggravation of airflow restriction. COPD patients' serum CCN1 levels had significant negative correlations with FEV1/FVC and FEV1% pred, respectively( all P<0.000 1). Serum CCN1 levels in COPD patients were negatively correlated with IgA, IgM and IgG, respectively (all P<0.000 1), and positively correlated with mDCs, pDCs and mDCs/pDCs, respectively( all P<0.000 1). ROC curve showed that AUC=0.883( 95%CI=0.744~0.955), the best prediction critical value was 40.15 ng/ml, and sensitivity and specificity were 89.0% and 77.8%, respectively. Conclusion: Serum CCN1 level in patients with smoking COPD increases and gradually increases with aggravation of airflow restriction, which is significantly correlated with decline of lung function and immune function, has a high predictive value for COPD, and is expected to become a potential biomarker for evaluation of COPD. [ABSTRACT FROM AUTHOR]