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Purpose: The principal focus of the study was exploring the hyperacute responses with respect to normal liver andthe change of assessment indexes for different observation times and radiation doses after total body X-irradiation exposures usingTibet mini-pig model.Methods and Materials: A total of 48 adult male Tibet mini-pigs were divided into six groups randomly.Five treatment groups (n=9) were irradiated with single dose of 2, 5, 8, 11 and 14-Gy total body irradiation respectively using a 8MvX-ray(isocenter) linear accelerator,and a dose rate of 255 cGy/min for each group.These pigs were tested by2-[18F]Fluoro-2}eoxy-D -glucose positron emission tomography with computed tomography and hepatic zymological test, andthen sacrificed by taking in carbon dioxide for pathologic test at 6, 24 and 72 hours (each time n=3) after irradiation respectively.Results: Radiation doses had highly significant effects on ail detecting indexes except CT values. Overall, the most obvious tendencyappeared at 24 hours after TBI and the most obvious change happened at 5 or 8 Gy. Hepatic standard uptake values (SUV) showedthe same tendency at relatively low doses (0-5 Gy) and the opposite tendency at relatively high doses (8-14 Gy)with pathology scoreand hepatocyte counting respectively；it showed the similar tendency with binucleated hepatocytes counting at 24 hours after TBI.Conclusion: (1) Normal liver was more sensitive than previous viewpoints and the hyperacute response of liver showed someregularity to radiation exposure. (2)5 Gy is a key dose. (3)[18F]-FDG-PET/CT had the potential to assess roughly the absorbedradiation dose, the conditions of metabolism aad severity of liver injury after radiation exposure as a sensitive and noninvasivemethod.