1. Brief medical history: Female, 59 years old, was admitted with dry cough and chest tightness for more than 2 months. Chest CT suggested: left upper lung mass shadow, intrinsic segmental bronchial invasion stenosis, local invasion of the left pulmonary artery trunk, and encapsulated artery in the apical anterior segment. Preoperative diagnosis: left upper lung cancer surgery: combined left upper lung bronchoplasty and pulmonary artery + mediastinal lymph node removal. 2.Surgical introduction: Exploration: no metastatic foci were seen in the pleura and no pleural fluid. The left pulmonary artery trunk was locally invaded, but the gap between the upper lobe bronchus and the left pulmonary artery trunk could still be successfully removed. The interlobular pleura was incised, the interlobular part of the pulmonary artery was freed and dissected, an artificial tunnel was established, the anterior and posterior parts of the oblique cleft were opened, 11 groups of lymph nodes were removed at the same time, the lingual segment artery and two posterior segment arteries were dissected and cut and tied. The tumor invaded one third of the circumference of the left pulmonary artery, and the length of invasion along the long axis of the pulmonary artery was about 0.5 cm. The operator blocked the distal and proximal ends of the pulmonary artery with a heart-ear clamp to make the invaded arterial segment bloodless, clipped the lateral wall of the invaded pulmonary artery and took part of the vessel wall to be sent for rapid freezing, and 5-0 Prilling thread was sutured continuously along the long axis to restore its continuity. The blocking forceps were released and there was no blood leakage, but the left pulmonary artery trunk was severely stenosed with a stenosis length of approximately 1.5 cm and a diameter of approximately 0.5 cm at the stenosis. The next intraoperative decision was the most exciting part of this procedure, and the final result is presented first: resection of the stenotic pulmonary artery segment, followed by end-to-end anastomosis to restore the continuity of the pulmonary artery. The reconstruction procedure was as follows: the left pulmonary artery root was blocked with potts clamp, the inferior pulmonary vein was blocked with romel, and the stenotic pulmonary artery segment was resected, then the distal end was trimmed into a bevel to increase its caliber, and then the two severed ends were sutured with 5-0 Prilling sutures in succession. During the suturing process, in order to prevent thrombosis, the vascular cavity should be flushed with heparin saline intermittently, and after the last stitch was sutured, the knot was held in abeyance, and the romel blocking the inferior pulmonary vein was released first, then the potts clamp was placed, and the knot was tied after exhaustion. Subsequently, another stitch was found to be cut in the vessel wall at the suture, and the surgeon took a 0.5 x 0.5 cm sized polyester patch (anti-cut) as a spacer to add stitches to repair the vessel laceration with good results. The later surgical steps were relatively simple, cutting the upper lobe bronchi and clearing groups 4, 5, 6, 7 and 8 lymph nodes to end the procedure. 3. Summary: The difficulty of this procedure was the intraoperative discovery of pulmonary artery trunk stenosis. The operator was faced with three options: no treatment, total lung resection, and reconstruction with sleeve resection of the pulmonary artery trunk. Obviously, the first two choices are inappropriate, but the third option also carries some risk that the tension of the anastomosis may be too high after reconstruction. If the excessive tension is still not relieved by releasing the inferior pulmonary ligament and hilar, then the operator has only one option – total left lung resection. Now back to the analysis, according to the intraoperative exploration of the tumor invasion of the left pulmonary artery, it is perfectly feasible to do a local arterial wall wedge resection, why would it cause post-reconstruction stenosis? There is only one answer: the vessel wall was cut too much. The operator used a cardiac ear clamp to block the distal and proximal ends of the left pulmonary artery. In fact, at this time, the cardiac ear clamp is equivalent to a lateral wall clamp, and after blocking the vessel, the operator was influenced by the blocking clamp during resection and often could not determine the remaining vessel wall, and in most cases, more cuts were made, resulting in post-reconstruction stenosis. Postoperatively, it was considered that a more satisfactory result might be obtained if a different type of intraoperative vascular block was performed before resection of the invaded vessel wall: the upper pulmonary vein was already cut, the left pulmonary artery root was blocked directly with potts clamp, the lower pulmonary vein was blocked by romel, and the stenotic pulmonary artery segment was removed without tension. Because this approach allows clear visualization of the remaining pulmonary artery wall during resection.