Objective    To examine anatomic features of the central myelin, the peripheral myelin and the transitional zone of trigeminal nerve.    Methods    Anatomical and histological techniques were used to investigate 15 adult cadaveric head specimens. The different skull base approaches were performed on those specimens under surgical microscope. The cistern segment of the nerves were embedded in paraffin and sectioned，for Luxol fast blue staining. The photomicrographs were used to measure the length of central myelin and transition zone.    Results    The central myelin extended into the cistern. About  (2.34±0.81)mm from the pons, the central myelin gradually transferred to peripheral myelin. The transition zone terminated at (3.78±0.69)mm from the pons. (30.5±5.6)% of the cistern segment of the trigeminal nerve composed of cental myelin, whereas the peripheral myelin formed aboudt (81.1±8.1)% of the cistern part. The TZ located at the site from (18.8±6.5)% to (30.5±5.6)% of the cisternal segment.    Conclusions    The extension of the central myelin and transition zone into the cistern gives the conception that REZ and TZ are distinct areas. The vascular compression in this region might be contributive to the trigeminal neuralgia.