〔Abstract〕 Objective To analyze the distribution characteristics of free water(FW) and FW-corrected fractional anisotropy(FAt) in the white matter of the brain in patients with anti-N-methyl-D-aspartate receptor(NMDAR) encephalitis and to explore their correlation with cognitive function. Methods A total of 38 patients with anti-NMDAR encephalitis and 30 controls were recruited from three hospitals in Hefei. Diffusion tensor imaging data and neuropsychological assessment results were collected. Tract-Based Spatial Statistics was applied to compare group differences in FW and FAt across the whole brain white matter. Correlation analyses were further performed to examine the relationships between FW/FAt metrics and cognitive function. Results Compared to the control group, patients with anti-NMDAR encephalitis showed significantly lower scores on the montreal cognitive assessment, immediate recall, delayed recall, and the verbal fluency test(all P