0bjective: To study the features and diagnostic value of MRI 3D-FIESTA-C (three-dimensional fast imaging employing steady state acquisition with cycled phases) and IDEAL (iterative decomposition of water and fat with echo asymmetry and least squares estimation）for traumatic brachial plexus injury. Methods: Thirty-two cases of traumatic brachial plexus injury were examined by MRI 3D-FIESTA-C and IDEAL sequences before operation. The imaging data were treated with post processing imaging. The diagnostic results were compared with the findings in operation. The value of MRI 3D-FIESTA-C and IDEAL sequences for diagnosing traumatic brachial plexus injury before operation was evaluated. Results: It revealed postoperatively that preganglionic brachial plexus injury occurred in 12 cases (39 nerves). The features of preganglionic brachial plexus injury in MRI 3D-FIESTA-C sequence included disappearance or disruption of nerve root(31), and decrease of nerve root filaments(7) with nerve root sleeve abnormality, meningeal cyst, sheath thickening and abnormal spinal cord signal. Compared with the findings in surgery, the sensitivity, specificity and accuracy of 3D-FIESTA-C sequence in diagnosing preganglionic brachial plexus injury were 97.5%, 100%, 98.3%, respectively. Postganglionic injury occurred in 31 cases (45 nerves), IDEAL sequence showed continuity interruption(42), and the others showed nerve trunk enlargement, distortion, rigidity, adjacent structure disorder and edema. Compared with the finding in surgery, the sensitivity, specificity and accuracy of IDEAL sequence in diagnosing postganglionic injury were 96.7%, 100%, 97.1%, respectively. Conclusions: MRI 3D-FIESTA-C and IDEAL sequences are excellent in revealing preganglionic brachial plexus injury and postganglionic injury. Their diagnosis accuracy rates are high. MRI is non-invasive and optimal for clinical diagnosis.