The sciatic nerve of 16 rabbits were examined with the optical and electron microscope 2, 24, 72 hours and 7 days after injecting penicillin (200,000 U) into nerve or its peripheral in experiment group and control group. The experiment group showed successively nerve fiber tumefaction, myelin sheath lamellar separation and degeneration partly, the construction of axonal change abnormality myelin and axonal obvious degeneration from 2 hours to 7 days. The control group showed perinerve edema, hyperemia, epineurium hyperplasia, the nerve fiber of near epineurium had mild pathologic changes.