Objective To observe the influence of gastroesophageal reflux disease (GERD) on pulmonary function of elderly male patients with chronic obstructive pulmonary disease (COPD). Methods A total of 158 elderly male patients (65 years old and above) with COPD were enrolled in this study, consisting of 41 patients with GERD (25.9%, positive group)and 117 patients without GERD ( negative group).The pulmonary function of two groups were compared. Results The mild COPD patients in positive group(2.4%)were apparently less than that of negative group（ 31.6% ）.However, the moderate（ 75.6% ） and severe 、very severe patients（ 22.0% ） were more than that of negative group（ 56.4% and 12.0% ）,The difference of severity of COPD between two groups was statistically significant（P＜0.001）. Compared with negative group, the forced vital capacity (FVC),the forced expiratory volume in 1 second(FEV1),the peak expiratory flow(PEF)，the maximal expiratory flow rate at 25% vital capacity（FEF25%）, the maximal expiratory flow rate at 75% vital capacity（FEF75%）were lower in positive group [（2.2±0.6）L vs．（2.6±0.6）L，（1.2±0.4）L vs．（1.5±0.4）L，（3.3±1.1）L/sec vs．（4.2±1.5）L/sec，（1.8±0.9）L/sec vs．（2.4±1.5）L/sec，（0.2±0.1）L/sec vs．（0.3±0.2）L/sec , Z = -4.443、-3.527、-3.350、-2.364、-2.061，respectively，all P<0．05]．Conclusion Comorbidity of GERD can influence the pulmonary function and the severity of disease on COPD patients.