Abstract: Objective The purpose of this study was to explore the serum total bilirubin (TBIL) level in the serum of chronic obstructive pulmonary disease (COPD) patients during acute exacerbation (AE) and correlation with pulmonary function . Methods The study population consisted of 73 AECOPD patients and 35 healthy controls . The levels of serum total bilirubin (TBIL) in both groups were determined for the comparison analysis. Pulmonary function parameters in both groups were also determined. Serum TBIL levels were measured both on the admission day and on the discharge day. Correlations of serum TBIL level on admission and functional and in?ammatory parameters were analyzed. Results S erum TBIL levels were significantly decreased in AECOPD patients compared to healthy subjects. 73 AECOPD patients included 17 patients in the intensive care unit (ICU) ，21 patients with respiratory?failure，24 patients in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1~2 group ，38 patients in GOLD 3 group and 11 patients in GOLD 4 group . Among all the hospitalized AECOPD patients, serum TBIL levels were significantly decreased in patients in ICU compared to patients not in ICU , and serum TBIL levels were significantly decreased in patients with respiratory?failure compared to patients not with respiratory?failure. The TBIL level were different (P<0.05) among GOLD 1~2 , 3, and 4 groups ( GOLD 1~2 >GOLD 3 >GOLD 4 group ). The TBIL levels on discharge were elevated compared to admission. The TBIL was positively correlated with FEV1 and FEV1/FVC (r= 0.911, 0.779, respectively, P<0.05). Conclusion Serum levels of TBIL might be related to disease outcomes in COPD patients. Serum TBIL levels were decreased during AECOPD , and were negatively correlated with the severity of disease. It is suggested that the measurement of serum TBIL is helpful for the evaluation of AECOPD.