A 24-year-old woman had been injured in an automobile accident. The chest X-ray showed widening of the mediastinum and computed tomography showed mediastinal hematoma around the aortic arch. Aortic rupture was suspected, so we performed aortography, which revealed pseudoaneurysm of the descending aorta. Moreover, she also had splenic rupture and pelvic fracture. She underwent an emergency operation 4 hours after the accident. Medial tear of the descending aorta was replaced with a graft under temporary bypass without heparin. Simultaneously, splenectomy was performed. Her postoperative course was uneventful. We consider that temporary bypass without heparin is a useful method during repair of the descending aortic rupture due to trauma.