Objective: To investigate the clinical efficacy of axillo-axillary crossover bypass grafting for subclavian steal syndrome and its effect on improvement of vertebral blood flow. Methods: The clinical data of 64 patients with arteriosclerotic subclavian steal syndrome undergoing axillo-axillary prosthetic bypass grafting over the past 7 years were retrospectively analyzed. Results: The success rate for bypass surgery was 100%, and no perioperative death occurred in the entire group. Five patients developed wound hematoma, 8 patients had symptoms of nerve injury, and no case of wound or graft infection was noted after surgery. Among the 55 patients followed up, the symptoms in 49 cases were improved, and vertebral blood flow improvement was seen in 94.87% (37/39) of the patients with stage IV retrograde vertebral flow and in 62.50% (5/8) of the patients with stage III retrograde vertebral flow, but no improvement was found in the two patients with stage II retrograde vertebral flow. No symptomatic improvement was observed after surgery in two patients, and 4 patients developed dizziness or limb numbness again during 3 to 25 months following surgery, and 5 of these 6 cases had improvement of vertebral blood flow. After surgery, the mean pressure gradient between upper limbs reverted to 10.22 mmHg, prosthetic thrombosis occurred in 4 cases and new cerebral infarction developed in 4 cases. Conclusion: Axillo-axillary crossover bypass grafting is a safe and effective procedure for patients with subclavian steal. This procedure can effectively improve blood flow in the vertebral artery, but the vertebral flow improvement is not always associated with symptomatic improvement.