Objective To find the optimal route of eontralateral C7 nerve transfer for brachial plexus avulsion injuries through autopsy. Methods The bilateral brachial plexus were exposed on 30 sides of 15 cadaverie specimens of adult. The C7 nerve root was sectioned at the junction site of trunk and division, and then dissected proximally to the foramina. The max length of anterior and posterior division of C7 was measured. The distance between the roof of C7 and the upper trunk and the lower trunk at the affected side through vertebral body route, prespinal route and a subcutaneous tunnel on the anterior surface of the neck was measured. Results The max length of anterior and posterior division of C7 was (7.67±1.06) cm and (7.79±1.36) cm respectively. The distance between the roof of C7 and the upper trunk at the affected side through vertebral body route, prespinal route and a subcutaneous tunnel on the anterior surface of the neck was (6.97±0.56) cm and (10.04±0.94) cm and (16.56±1.24) cm respectively, there were statistical significance among them (P < 0.01). The distance between the roof of C7 and the lower trunk at the affected side through vertebral body route and prespinal route and a subcutaneous tunnel on the anterior surface of the neck was (6.82±0.92) cm、(9.91±0. 83) cm and (17.64±0.97) cm, with a significant difference (P<0.01). Conclusion The best way of contralateral C7 nerve transfer for the treatment of brachial plexus injury was through the vertebral body route from the point of anatomy.