Objective: To analyze the clinical value of simultaneous ¹⁸F-FDG PET/MR imaging(PET/MRI) in precise localization of epileptogenic lesion. Methods: Twenty-five patients with drug-refractory epilepsy were enrolled.All patients underwent simultaneous PET/MR during the interval of epilepsy. The epileptogenic foci were identified by stereo-tactic electroencephalography (SEEG) or surgical pathology in all patients within one month after PET/MRI. The sensitivity and specificity of three imaging modalities including single MRI, single PET and PET/MRI in localizing epileptogenic foci were compared. The standard deviation (SD) values of each brain region were assessed by matching the epileptogenic foci with the normal PET/MR brain metabolic database by MI Neurology software. The differences of SD values and mean standardized uptake value mean (SUVmean) between the lesions and the oppositesite brain regions were compared. Results: The sensitivity and specificity of single MRI in locating epileptogenic focus were 37.5% (9/24) and 100% (4/4), respectively. There were 15 epileptogenic focus which could not be displayed by single MR, among which there were fourteen focus with no structure abnormal. PET/MRI can detected twelve of these fourteen lesions and the sensitivity of PET/MRI in localizing epileptogenic foci was 91.6% (22/24), which was significantly higher than that of single MRI (P< 0.05). The specificity of PET/MRI was 100%. The combination of PET and MRI reduced false-positive diagnosis. At the same time, MRI could provide a very clear anatomical structure and help foraccurate localization. The SD value of epileptogenic foci was -6.16+2.26 and that of opposite healthy side was -0.72+0.89. The SD value of epileptogenic lesion was significantly lower than that of control area (P<0.01). Conclusions: Simultaneous PET/MRI fully combines the advantages of two imaging methods. For the nonstructural abnormal epileptogenic foci, combined MRI with PET (including quantitative PET) can detect the MRI-negative foci, and with the high resolution and clear defining of anatomical structure, MRI combined with PET can accurately evaluate the location and scope of the foci on the same machine, which provides great help to design surgical therapy plan and denotes great application prospect in the individualized and precise medical treatment of epilepsy.