Objective To observe the correctly positioning rate of left-sided double lumen endobronchial tube by combined adjustment of auscultation,PETCO2 and airway pressure changes.Methods Sixty adult patients undergoing thoracic surgery were intubated with Robertshaw DLTs. DLT position is checked and adjusted by fiberoptic bronchoscope（FOB）. Results In the supine position,successful intubation is 57 cases by three combined methods,one of cases is shallower,two of cases are deeper,satisfactory rate is 95 percents;In the lateral decubitus position,successful intobution is 56 cases by three combined methods,two of cases is shallower,two of cases are deeper,satisfactory rate is 93.4 percents.Conclusion Three combined methods that are simple,reliable can be used repeatedly during postural changes without increasing the opportunities for injury,it is clinically a very good approach,but the absolute scope of safety is very small,FOB is necessary for positioning.