目的　为侧颅底手术中面神经乳突段的定位提供解剖学资料。  方法　 10%福尔马林固定成人头颅标本8例16侧，电动磨钻轮廓化乳突，暴露3个半规管、面神经乳突段全长。测量面神经乳突段的长度、宽度、面神经乳突段始端及末端与周围重要结构的距离，并观察面神经乳突段与周围毗邻结构的关系。  结果　面神经乳突段的长度为（11.04±1.03）mm，宽度为（2.29±0.39）mm。面神经乳突段起始部到乙状窦、外耳道后上棘、颅后窝硬膜、岩上窦-乙状窦-横窦交点、后骨半规管的最近距离分别为（9.41±　2.06）mm、（15.61±2.11）mm、（5.96±1.51）mm、（20.20±3.44）mm、（3.84±0.14）mm。面神经乳突段末端-乙状窦 、外耳道后上棘、乳突尖、颅后窝硬膜、岩上窦-乙状窦-横窦交点的最近距离分别为（7.05±2.01）mm、（20.32±2.69）mm、（16.48±2.48）mm、（7.97±2.61）mm、27.38±4.21)mm。  结论　外骨半规管、后骨半规管、二腹肌嵴是面神经乳突段定位的重要标志，面神经乳突段走行于外骨半规管、后骨半规管和二腹肌嵴前端形成的三角形内。

Objectives　 To provide anatomic data for identifying the mastoid segment of facial nerve during mastoidectomy through the lateral approaches.　Methods　The research was applied on 8 cadaveric specimens. Electric drill was used to remove the superficial bone of the mastoid process to expose the underlying semicircular canals and the mastoid segment of the facial nerve. The length and diameter of the vertical segment of the facial nerve were measured. The distances from the vertical segment of the facial nerve to surrounding structures were measured.　Results　The length of the mastoid segment of the facial nerve was about （11.04±1.03）mm，and the diameter （2.29±0.39）mm. The distance from the beginning of the mastoid segment of the facial nerve to sigmoid sinus, Helen's spine, durra mater of the posterior fossa, the junction of sigmoid sinus and transverse sinus, posterior semicircular canal was（9.41±2.06）mm,（15.61±2.11）mm,（5.96±1.51）mm,（20.20±3.44）mm,（3.84±0.14）mm separately. The distance from the end of the mastoid segment of the facial nerve to the sigmoid sinus, Helen's spine, mastoid tip, durra mater of the posterior fossa, the junction of sigmoid sinus and transverse sinus was（7.05±2.01）mm,（20.32±2.69）mm,（16.48±2.48）mm,（7.97±2.61）mm, and (27.38±4.21)mm respectively.　Conclusions　Horizontal semicircular canal, posterior semicircular canal and the digastric ridge are important structures for identifying the mastoid segment of the facial nerve. The mastoid segment of facial nerve lies in the triangle formed by the posterior semicircular canal, the horizontal semicircular canal and the anterior edge of the digastric ridge.