Pacemaker implantation via subclavian venipection is a common procedure.A patient who had a pacemaker implanted via subclavian venipection developed a massive hemothorax 21 hours after surgery.The video-assisted thoracic surgery(VATS) showed that the left subclavian artery branch ruptured and bled,and titanium clip was used to clamp and stop bleeding. For patients with difficulty in puncture process,even if it is confirmed that the device is inserted into the subclavian vein,it is important to be vigilant against damaging adjacent arteries in the process, and strict electrocardiograph monitoring should be conducted after surgery. Once hemothorax appears,VATS should be performed in conjunction with the surgeon to locate the bleeding point and stop the bleeding.