Purpose: The purpose of this study were to analysis the effect on change of spinal neuron excitability during gait training of hemiplegia patients by the functional electrical stimulation. Methods: Thirty six hemiplegia patients participated in this study. Stimulation conditions of FES were pulse rate 35pps, pulse width $250{mu}s$, and on-time 0.3 second, treatment hour was 30 min. and treatment period was once a day for five days a week through six weeks. For functional evaluations before and after treatment, Modified Ashworth Scale (MAS), active range of motion (AROM), Hmax threshold, H/Mmax ratio were measured and the following conclusions were obtained. Results: Functional evaluation showed significant changes in experimental group as MAS(p<0.01), AROM(p<0.001), compared to control group. In spinal neuron excitability evaluation, change of Hmax threshold was significantly reduced in both non weight bearing (p<0.001) and bearing condition (p<0.05), H/Mmax ratio was significantly reduced in non weight bearing (p<0.05) and bearing condition (p<0.05). Conclusion: In conclusion, application of FES to hemiplegia patients in recovery stage during gait training improved mitigation of muscular spasticity, balance adjustment and moving ability and it was interpreted that it was caused by mitigation of muscular spasticity by the spinal neuron excitability.