〔Abstract〕 Objective To investigate the spontaneous activity of neurons in the resting state of patients exposed to car accident trauma. Methods 17 patients with posttraumatic stress disorder(PTSD group) and 23 patients without PTSD(non-PTSD group) after car accident trauma exposure were included in the study. The differences in fractional low-frequency amplitude(fALFF) between the PTSD and non-PTSD groups at 1 week and 2 months after the traumatic event were compared horizontally,and the PTSD and non-PTSD groups were compared longitudinally before and after fALFF at 1 week and 2 months after the traumatic event. Results Compared with the non-PTSD group,fALFF in the PTSD group decreased in the left posterior central gyrus after traumatic event at 1 week, fALFF in the PTSD group decreased in the left medial frontal gyrus at 2 months(P<0.01,GRF correction), and no abnormality was found in the residual brain areas. In the PTSD group, compared with the first week, fALFF significantly increased in the right medial temporal gyrus and left occipital lobe at 2 months after the traumatic event. In the non PTSD group, compared with the first week,fALFF decreased in the left cerebellum and left posterior cingulate gyrus and increased in the right precuneus at 2 months after the traumatic event(P<0.01, GRF correction), and no abnormality was found in the residual brain areas. Conclusion fALFF changes in the brain of patients with PTSD may be related to the pathophysiological mechanism of PTSD, which is helpful for early diagnosis and intervention of PTSD.