Objective To preliminarily investigate the correlation between diffusion tensor imaging (DTI) parameters of the ascending reticular activating system (ARAS) and prognosis in patient with coma after traumatic brain injury (TBI).Methods Patients with coma after TBI in the last three years were selected as research subjects. DTI and diffusion tensor tractography of the ARAS were performed at 3 and 5 weeks after TBI. Two regions of interest (ROIs) for reconstruction of the ARAS were the seed ROIs-the midbrain and the tegmental region of the pons and the target ROI-the thalamic intralaminar nuclei. The fractional anisotropy (FA), mean diffusivity (MD), and tract volume (TV) of the ARAS fiber tracts were systematically analyzed and the correlation between the changes of ARAS fiber tracts and the consciousness status of the patients at 3 months after TBI was analyzed. A Spearman correlation analysis was used to analyze the correlation between FA, MD, and TV and prognostic score.Results There was no correlation between the FA and MD of the ARAS at 3 weeks after TBI and the prognosis at 3 months after TBI (P>0.05), while there was a significant correlation between the TV of the ARAS at 3 weeks after TBI and the prognosis at 3 months after TBI (r=0.89,P<0.001). The prognosis at 3 months after TBI was positively correlated with the FA and TV of the ARAS at 5 weeks after TBI (P<0.001;P<0.001). The Glasgow Coma Scale score and Glasgow Outcome Scale score at 3 months after TBI were positively correlated with the changes in FA and TV from 3 to 5 weeks after TBI (P<0.005;P<0.05;P<0.001;P<0.001).Conclusions The consciousness status of patients with coma at 3 months after TBI is correlated with the DTI simulated FA, MD, and TV of the ARAS and their changes at 5 weeks after TBI. The changes of the ARAS fiber tracts in subacute phase can indirectly reflect patients' ability to recover consciousness.