Abstract:[Objective] To evaluate the efficacy and safety of phrenic nerve transfer to the posterior bundle of inferior trunk of forelimb plexus (PBITFLP) to regain toe extension function in rats. [Methods] Twenty-four SD rats were randomly divided into 4 groups with 6 rats in each group. In the end-to-side anastomosis (the E-S group) , the phrenic nerve was anastomosed with the saphenous nerve graft by end-toside, and then transferred to PBITFLP. In the end-to-end anastomosis (the E-E group) , phrenic nerve was cut off and anastomosed with sa- phenous nerve graft by end-to-end suture, and transferred to PBITFLP. In situ anastomosis (the ISA group) , the PBITFLP was cut and then sutured in situ. In unrepaired anastomosis (the UR group) , the PBITFLP was cut only without anastomosis. Function observation, electro- physiological examination and reverse fluorescence tracer of the deep branch of radial nerve or posterior bundle of inferior trunk were con- ducted and compared among the 4 groups. [Results] At 7 weeks after operation, compound muscle action potential (CMAP) was recorded in the toe common extensor after stimulation of phrenic nerve in both the E-S group and the E-E group, which was not statistically significant in terms of amplitude and latency of CMAP between the two groups (P>0.05) . In the ISA group CMAP was detected in the extensor by stimu- lation of the PBITFLP, in which the amplitude and latency of CMAP were significantly greater than those in the E-S and E-E groups (P< 0.05) . In addition, CMAP was detected in the diaphragm by stimulation in the E-S, ISA, and UR groups, without statistically significant dif- ferences in amplitude and latency among the groups (P>0.05) . In terms of nerve tracer detection, positive cells were found in anterior horn of C3/4 from deep branch of radial nerve in both the E-S group and E-E group, which in the E-E group was significantly greater than the E-S group (P<0.05) . On the other hand, the number of positive cells traced from the deep branch of the radial nerve in the healthy side to the an- terior horn of C8T1 in the E-S group and the E-E group was significantly higher than those in the ISA group and UR group (P<0.05) . [Conclusion] The end-to-side phrenic nerve transfer is safe and effective for restoring the function of toe extensor partially in this rat experiment.