Objective To explore the effect for nerve regeneration with immunosuppresssant FK506 a-round the cut after end-to-side neurorrhaphy of peripheral nerve. Methods There were 40 adult SD rats and were divided into two groups randomly by means. In the experiment group, the right peroneal nerve of SD rat was cut off,then an 1mm epineural window was created on the neighboring tibial nerve,the distal end of peroneal nerve was sutured to the windowed tibial nerve by means of end-to-side attachment, application of slow-releasing diaphragm which was implanted around the nerve anastomosis with FK506. In the contrast group,there were not the FK506 around the cut after end-to-side neurorrhaphy. The tibial and peroneal nerve trunks were labeled by being in jected with fast blue ( KB) and fluorescence golden ( FG) respectively. The labeled cells in the dorsal root ganglia (DRG) and spinal cord were observed by fluorescence microscopy. Results There were a lot of FB labeled cells in the experiment group than in the contrast group in the DRG and spinal cord. Conclusion Immunosuppresssant FK506 could promote nerve regenerative speed and quality after end-to-side neurorrhaphy of peripheral nerve.