Objective：To investigate the therapeutic effect of tiotropium bromide in combination with nocturnal oxygen therapy on nocturnal hypoxemia in patients with chronic obstructive pulmonary disease（COPD） and to evaluate indirectly the efficacy of tiotropi－um bromide for nocturnal hypoxemia. Methods：Totally 40 patients with stable moderate to severe COPD and nocturnal hypoxemia were recruited and randomly divided into the observation group （n=20） and the control group （n=20）. The patients in the observation group were given inhalative tiotropium bromide（18 μg，once every afternoon） in combination with nocturnal oxygen therapy（2 L/min） while those in the control group were treated with nocturnal oxygen therapy（2 L/min） only. Nocturnal oxygen saturation （SaO2），arte－rial blood gases and pulmonary function were examined before and four weeks after the treatment. Results：After the treatment，noc－turnal mean SaO2 （MSaO2），nocturnal minimum SaO2 （MmSaO2），arterial partial pressure of oxygen （PaO2），arterial SaO2，first second forced expiratory volume（FEV1），percentage of FEV1 in the predicted value （FEV1%Pred），forced vital capacity（FVC），forced inspira－tory capacity （IC） and percentage of peak expiratory flow rate in the predicted value （PEF%Pred） were significantly increased in the observation group. In the control group，MSaO2，MmSaO2，PaO2 and SaO2 were significantly increased，but no change in FEV1，FEV1%Pred，FVC，IC and PEF%Pred was observed. Both groups showed significant decreases in the percentage of the time with noc－turnal SaO2<90% in the total sleep time （T90）. Arterial partial pressure of carbon dioxide （PaCO2） was significantly decreased in the observation group；however it was remarkably increased in the control group. After the treatment in the observation group，MSaO2，MmSaO2，PaO2 and SaO2 were significantly increased；T90 and PaCO2 were significantly decreased；FEV1，FEV1%Pred，FVC，IC and PEF%Pred were notably increased compared with those in the control group. Conclusion：Tiotropium bromide in combination with nocturnal oxygen therapy could significantly improve the symptoms of nocturnal hypoxemia in patients with stable COPD，which is su－perior to nocturnal oxygen therapy alone. Meanwhile，tiotropium bromide could also improve the symptoms of nocturnal hypoxemia in patients with stable COPD.