Abstract: Objective To investigate the effects of dexmedetomidine infusion during one-lung ventilation (OLV) on oxygenation and respiratory mechanics in elderly patients undergoing thoracoscopic lung surgery. Methods A total of 158 elderly patients undergoing video-assisted thoracoscopic surgery (VATS) from November 2015 to November 2018 for lobectomy were selected and divided into observation group (80 cases) and control group (78 cases) according to the principle of random number method. The observation group was given dexmedetomidine hydrochloride pump during operation, while the control group was given physiological salt pump. The differences of oxygenation index, respiratory mechanics index and hemodynamics index at different time between the two groups were analyzed. The hypoxemia during operation and pulmonary complications after operation were observed. Results PaO₂/FiO₂ at T1 and T2 were significantly higher in the observation group than in the control group， There was no statistical significance (all P>0.05). There were no cases of hypoxemia in the two groups, and the incidence of pulmonary complications in the observation group (0.00%) was significantly lower than that in the control group (11.54%, χ²=7.758, P=0.005). Conclusion The infusion of dexmedetomidine during OLV in elderly patients undergoing VATS is helpful to improve respiratory mechanics, increase oxygenation capacity and reduce the incidence of pulmonary complications. It is worthy of clinical application.