Objective To determine the effect of gastroesophageal reflux disease (GERD) on pulmonary function in the elderly male patients with chronic obstructive pulmonary disease (COPD). Methods A retrospective study was carried out on 158 elderly male COPD patients (≥65 years old) with whole results of pulmonary function test and clinical data who admitted in Geriatric Department of our hospital from February 2002 to January 2016. According to complicated with GERD or not, they were divided into GERD group (n=41) and non-GERD group (n=117). The pulmonary functions were compared between the 2 groups. Results The severity of COPD was significantly severer in the GERD group than the non-GERD group (P<0.05). Compared with the non-GERD group, the forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), peak expiratory flow (PEF), the forced mid-expiratory flow (FEF25%-75%), forced expiratory flow after 25% of FVC has been exhaled (FEF25%), forced expiratory flow rate at 50% vital capacity (FEF50%) and forced expiratory flow after 75% of FVC has been exhaled (FEF75%) were significantly lower in the GERD group (P<0.05). Conclusion Complication of GERD affects the pulmonary function and severity in the COPD patients.