Objective To study the effect and pathological mechanisms of the neuro-immune response of viral encephalomyelitis caused by the virulence reversion of the intrathalamic neurovirulence test of poliomyelitis vaccine in rhesus macaques. Methods The stock solution (not less than 7000 lgCCID50?L-1) of the inactivated polio vaccine (Vero cells) of type I, type II and type III Sabin strains and 10-1 dilution of each type of polio vaccine were carried out using intrathalamic neurovirulence test. We observed the pathological changes of polio. Via immunohistochemical method, the distribution of receptor CD155 and CD4+ T lymphocytes, CD20+ B lymphocytes and CD68+ microglia were detected. Results Lesions were observed on the virulence reverted polio case. Inflammatory cells infiltrating, neuronal degeneration and necrosis, satellite phenomenon, perivascular cuffing and glial cell proliferation were observed in the spinal cord. The inflammatory cells were mainly CD4+ T lymphocytes, CD20+ B lymphocytes, and CD68+ microglia in perivascular cuffing and proliferative glial nodules. There is no significant difference on distribution of poliovirus receptor CD155 in neurons and glial cells of monkeys with and without polio, while no expression was observed in vascular endothelial cells. Conclusion Polio caused by virulence reversion of the intrathalamic neurovirulence test is viral encephalomyelitis.