Objective To investigate the value of 3.0T magnetic resonance imaging (MRI) in diagnosis of severe traumatic brain injury and outcome prediction. Methods Thirty-eight patients with severe traumatic brain injury were evaluated with MRI 4 to 6 weeks after injury, the lesion volumes in T1 and T2 weighted imaging and fluid attenuated inversion recovery (FLAIR) images were quantified and compared with simultaneous CT findings. The diffuse axonal injury (DAI) scores were recorded, and correlation analysis was performed with Glasgow coma scale (GCS) on admission and Glasgow outcome scale (GOS) 6 months after injury. Results MRI demonstrated more lesions than CT, especially for the corpus callosum and brain stem lesions. There were significant differences in DAI scores and lesion volumes in T1 and T2 weighted imaging and FLAIR images between different outcome groups (P<0.05). DAI score had strongest correlation with GOS 6 months after injury (r=－0.854, P<0.05), and the lesion volume detected by MRI was also negatively correlated with the outcome （P<0.05). Conclusion 3.0T MRI is superior to CT in detection of intraparenchymal injury, especially for deep lesions. A quantitative study of the lesion volume and location demonstrated by MRI may play a role in outcome prediction.