Objective To investigate the serum level of C1q tumor necrosis factor-related protein 9 (CTRP- 9) in patients with chronic obstructive pulmonary disease and its clinical significance. Methods A total of 90 stable patients with chronic obstructive pulmonary disease who were present in our hospital from October 2016 to October 2017 were selected as the observation group. In the same period, 90 healthy residents who were physically examined in our hospital were selected as the control group. The serum levels of CTRP-9 were determined by enzyme-linked immunosorbent assay. Forced expiratory volume in 1st second as percentage of predicted values (FEV1%pred) of two groups were measured by spirometer, and analyzed with the serum levels of CTRP-9 for their correlation. Results The serum CTRP-9 level in the observation group was significantly higher than that in the control group (P < 0.05). The FEV1%pred of the observation group was significantly lower than that of the control group (P < 0.05). The results of the Person correlation analysis showed that the serum level of CTRP-9 was negatively correlated with FEV1%pred (r = -0.803, P = 0.004). Conclusions CTRP-9 is highly expressed in the serum of patients with chronic obstructive pulmonary disease, and the level of its expression is correlated with lung function of patients.