Objective to investigate the efficacy and safety of the end to side transfer of phrenic nerve to the posterior division of lower trunk in the recovery of toe extension. Methods 24 SD rats were divided into 4 groups with 6 rats in each group. In group A, the phrenic nerve was transferred end to side through the saphenous nerve to the posterior division of the lower trunk. In group B, the phrenic nerve was transected and transferred to the posterior division of the lower trunk through the saphenous nerve. Group C: direct repair: the posterior division of lower trunk was cut off and was sutured directly. Group D: the posterior division of lower trunk was not repaired after cutting off. The function, electrophysiological examination, retrograde fluorescence tracing of the deep branch of radial nerve and the posterior division of lower trunk，the fluorogold positive neurons were observed in Spinal cord segment. Results There was significant difference in amplitude between A,B two groups, but not in latency，in group C CMAP was recorded in the extensor digitorum communis muscle after stimulate the posterior division of lower trunk，The amplitude and latency were better than A,B two groups, and the difference was statistically significant. CMAP was recorded in diaphragm in A,C,D groups, there was no significant difference in amplitude and latency among the groups. There were more positive cells in the anterior horn of c3c4 spinal cord in group B than in group A, and the difference was statistically significant,The number of positive cells from deep branch of radial nerve to c8t1 spinal cord segment in group C was more than that from group AB to c3c4 spinal cord segment, and the difference was statistically significant. Conclusion It is safe and effective to partially recover the function of toe extension with phrenic nerve end to side transfer to repair the posterior division of lower trunk.