【Abstract】 Objective To investigate the feasibil ity of contralateral C7 nerve transfer via posterior spinal route fortreatment of brachial plexus root avulsion injury by anatomical study. Methods Ten cadaveric specimens of 7 men and3 women were selected, who had no obvious deformity and no tissue defect in neck neutral position. By simulating surgical exploration of brachial plexus injury, the length of contralateral C7 nerve root was elongated by dissecting its anterior and posterior divisions to the distal end, while the length of C7 nerve from the intervertebral foramen to the branching point and the length of the anterior and posterior divisions were measured. By simulating cervical posterior approach, the C7 vertebral plate and T1 spinous process were fully exposed; the hole was made near vertebral body; and the C7 nerve root lengths by posterior vertebra path to the contralateral upper trunk and lower trunk were measured. Results C7 nerve root length was (58.62 ± 8.70) mm; the length of C7 nerve root plus posterior or anterior division was (65.15 ± 9.11) mm and (70.03 ± 10.79) mm, respectively. By posterior spinal route, the distance was (72.12 ± 10.22) mm from the end of C7 nerve to the contralateral upper trunk of brachial plexus, and was (95.21 ± 12.50) mm to the contralateral lower trunk of brachial plexus. Conclusion Contralateral C7 nerve can be transferred to the contralateral side through posterior spinal route and it only needs short bridge nerve or no. The posterior spinal route can effectively prevent from neurovascular injury, so it might be the best surgery approach for the treatment of brachial plexus root avulsion injury.