Objective To observe the recovery of the sensory and motor function of the repaired l imb and the impact on the healthy l imb function after contralateral C7 nerve root transposition for treating brachial plexus root avulsion injury. Methods Between August 2008 and November 2010, 22 patients with brachial plexus root avulsion injuries were treated with contralateral C7 nerve root transposition. All patients were male, aged 14 to 47 years (mean, 33.3 years). Total brachialplexus root avulsion was confirmed by preoperative cl inical examination and electrophysiological tests. In 22 cases, median nerve was repaired in 16 cases, radial nerve in 3 cases, and musculocutaneous nerve in 3 cases; primary operation was performed in 2 patients, and two-stage operation was performed in 20 patients. The sensory and motor functional recovery of the repaired limb was observed after operation. Results Twenty-one patients were followed up 7-25 months (mean, 18.4 months). In 16 cases of contralateral C7 nerve root transposition to the median nerve, wrist flexors reached more than M3 in 10 cases, while finger flexors reached more than M3 in 7 cases; sensation reached more than S3 in 11 cases. In 3 cases of contralateral C7 nerve root transposition to the musculocutaneous nerve, elbow flexors reached more than M3 in 2 cases; sensation reached more than S3 in 2 cases. In 3 cases of contralateral C7 nerve root transposition to the radial nerve, wrist extensor reached more than M3 in 1 case; sensation reached more than S3 in 1 case. Conclusion Contralateral C7 nerve root transposition is a good procedure for the treatment of brachial plexus root avulsion injury. Staged operation is one of important factors influencing treatment outcome.