Objective To investigate the safety and efficacy of Onyx endovascular embolization in the treatment of acute massive hemoptysis. Methods Between Mar. 2015 and Aug. 2017, a total of 20 patients with acute massive hemoptysis received Onyx endovascular embolization in our hospital, including 14 males and 6 females, with a median age of 45.5 years (ranged 17-73 years), 10 cases of bronchiectasis, 3 cases of pulmonary tuberculosis, 2 cases of lung cancer, 1 case of arteriovenous malformation and 4 cases of cryptogenic hemoptysis. There were 10 cases experienced rebleeding after embolization with conventional agents within 7 days (transfered from other hospitals). The technical and clinical success rates and the related complications of Onyx endovascular embolization in treating acute massive hemoptysis were analyzed. The short-term (<3 months), medium-term (3-< 12 months) and long-term (≥ 12 months) recurrence rates were calculated. Results Embolization was technically and clinically successful in all the 20 patients (100.0%) and postoperative bleeding was effectively controlled. No serious complications such as spinal cord injury or respiratory failure occurred. The median follow-up time was 22.5 months (3-42 months), and 18 patients (90.0%) were followed up for more than 12 months. Three patients experienced recurrent hemoptysis at 1 month, 7 months and 15 months after initial embolization; all of them were treated effectively by internal medicine, and no further interventional hemostasis was given. Two cases died from the primary tumor of the lung at 4 months and 10 months after embolization. The recurrence rates of short-term (<3 months), medium-term (3-<12 months) and long-term (≥ 12 months) were 5.0% (1/20), 5.0% (1/20) and 5.6% (1/18), respectively. Conclusion Onyx endovascular embolization is safe and effective in the treatment of acute massive hemoptysis.