Vascular injury is the most life-threatening complication under thoracoscopic surgery. To reduce the risk of vascular injury, knowledge of the anatomy of the pulmonary artery, variations in its branching, skillful techniques and careful maneuver are necessary. Pulmonary artery being adherent to bronchus is dangerous to dissect under thoracoscopy, so it is better to convert to open thoracotomy. A3 of the left upper lobe is occasionally injured during dissection. It is a safety technique for using vascular stapler under thoracoscopic surgery. Stapler leader can allow the passage of a stapler to encircle the vessel.