Objective: To investigate the brain function and structural characteristics of anti-leucine-rich glial inactivating protein 1(LGI1) antibody autoimmune encephalitis based on functional magnetic resonance imaging(fMRI) and diffusion tensor imaging(DTI), in order to provide ideas for understanding the neuropathological mechanism of anti-LGI1 antibody autoimmune encephalitis. Methods: Twenty-five patients with anti-LGI1 antibody autoimmune encephalitis admitted to our hospital from August 2019 to July 2022 were selected as the research group, and 25 volunteers without brain disease recruited during the same period were selected as the control group. Fifty subjects were evaluated by scale, fMRI and DTI respectively. Reagional homogeneity(ReHo) analysis was performed based on fMRI examination, and white matter fiber structure was analyzed based on DTI examination results. Results: The score of Modified Rankin Scale(mRS) in the study group was significantly higher than that in the control group(P<0.05). The scores of the Mini-Mental State Examination(MMES) and Montreal Cognitive Assessment(MoCA) in the study group were significantly lower than those in the control group(P<0.05).The ReHo of the right superior temporal gyrus, right middle temporal gyrus and left caudate nucleus of the subjects in the study group were significantly lower than those in the control group(P<0.05). The fractional anisotropy(FA) of the anterior radial crown, the upper radial crown, the posterior radial crown, the anterior limb of the inner capsule, the posterior part of the lens of the inner capsule, the posterior part of the thalamus, the outer capsule, the upper longitudinal bundle, the compression part of the corpus callosum, the corpus callosum, and the knee of the corpus callosum in the study group were lower than those in the control group, and the mean diffusivity(MD) of these parts were higher than those in the control group(P<0.05). Conclusion: Patients with anti-LGI1 antibody autoimmune encephalitis may experience the decline of memory function, cognitive function and motor function in brain function, which is related to the existence of extensive white matter fibrosis in the brain.