Objective To evaluate the effect of dexmedetomidine on pulmonary function in elderly patients with mild obstructive ventilatory dysfunction under protective ventilation during laparoseopic gallbladder surgery. Methods Sixty patients were included who underwent laparoseopic gallbladder surgery with general anesthesia. For the all subjects, the age ranged from 65 to 75 years old, the body mass index range was 18.5～23.9 kg/m2, and the ASA grade wasⅡorⅢ. In the subject selection, the gender was not limited, and the included subjects were diagnosed with mild obstructive ventilation dysfunction by preoperative pulmonary function tests. All the subjects were randomly divided into 2 groups (n=30), including dexmedetomidine group (group D) and control group (group C). In the group D, dexmedetomidine was intravenously infused at a dose of 1 μg/kg 10 min before and after the general anesthesia induction, and at a rate of 0.4μg/(kg·h) after tracheal intubation until the end of operation. Group C was given an equal volume of normal saline. Airway peak pressure (Ppeak), mean airway pressure (Pmean), airway plateau pressure (Pplat), and positive end-expiratory pressure (PEEP) were measured at 5 min after intubation (before pneumoperitoneum) (T1), end of pneumoperjtoneum (T2), and 10 min after the end of pneumoperitoneum (T3). The driving pressure (DP) was calculated. The blood samples of the radial artery were collected for blood gas analysis, and PaO2 and PaCO2 were recorded. The oxygenation index (PaO2/FiO2), respiratory index (RI), dead space ventilation rate (VD/VT), and alveolar-arterial oxygen partial pressure difference (A-aDO2) were calculated. The time of removal of the tracheal tube and the occurrences of complications such as hypercapnia and hypoxemia within 48 hours after extubation were recorded. Results Compared with group C, Ppeak, Pmean, DP, RI, VD/VT and A-aDO2 at T1, T2, T3 were decreased in group D, PaO2/FiO2 was increased, postoperative extubation time was shortened, and the incidence of hypoxemia was reduced within 48 h after operation (P<0.05). Compared with T1, Ppeak, Pmean, DP, RI, VD/VT and A-aDO2 at T2 were increased, and PaO2/FiO2 was decreased(P<0.05). Conclusions Dexmedetomidine can improve the pulmonary function in elderly patients with mild obstructive ventilatory dysfunction under protective ventilation during laparoseopic gallbladder surgery.