Objective：To investigate the immediate effects of vagal nerve stimulation（VNS）on the brain functional connectivity of patients with drug-resistant epilepsy（DRE）and explore the mechanism by whichVNS inhibits epileptic seizures. Methods： Magnetoencephalography（MEG）data were collected from 14 healthy subjects in a resting state and from 14 DRE patients in both resting and stimulated states. The changes in brain functional connectivity induced by immediate VNS were analyzed in six frequency bands. Results：In the resting state，DRE patients showed significantly enhanced functional connectivity compared to healthy subjects. When VNS occurred，DRE patients exhibited significantly reduced functional connectivity，including the connections between the left middle frontal gyrus and the right olfactory cortex and the connections between the left thalamus and the surrounding cortex of the right calcarine fissure in the theta frequency band，and the connections between the left thalamus and the left temporal polar middle temporal gyrus in the alpha frequency band. Conclusion：Immediate VNS can reduce the brain functional connectivity of DRE patients，thereby reducing the vulnerability of the brain network to seizures. This might be an important mechanism by which VNS modulates the inhibition of epileptic seizures in DRE patients.