Objective To observe and measure the anatomical structure of approach of vertical facial nerve canal and put forward the normal measurement range and the location relationship among the vertical segment of facial nerve canal, the posterior wall of external acoustic meatus and the rear edge of external ear，and discuss the relationship and clinical significance between the mastoid gasification and the vertical segment of facial nerve canal. Methods 1. Evaluate the accuracy of CT image of related structure, using spiral CT in scanning four skull specimens, get the horizontal distances of the vertical segment of facial nerve canal to the posterior wall of external acoustic meatus and the rear edge of external in the axial position, and get the sagittal diameter of mastoid (the horizontal distance from the lowest point of external auditory inferior canal to the rear edge of mastoid) and the height (the vertical distance between the lowest points of the external auditory canal wall to the mastoid tip) in the sagittal position. And then saw the skull specimens to measure the distance in the same lay with CT image, and discuss the statistics difference of the distance between the values of CT imaging measurements and the dry entities cranial measurements on hand. 2. Study on people: 118 patients (236 sides) with nonear disorders were randomly selected, among which there were 63 females (126 sides) and 55 males (110 sides). They were subjected to maxillofacial CT scan in the same layer that used above, and the horizontal distances of the facial nerve canal to the posterior wall of external acoustic meatus and the rear edge of external ear were measured. In addition, half of the product of diameter and height of the mastoid was defined as mastoid area, which was used to define the extension of mastoid gasification. Then related analysis and regression analysis were done between the vertical segment of facial nerve canal and the posterior wall of external acoustic meatus, as well as the rear edge of external ear. Results 1.Part of the experiment: There was no significantly different on the indicator values between CT image the entity measurements among the four skull specimens (P>0.05). 2. Study on people: There was no significantly different between left side and right side(EM>P/EM>>0.05), but significantly different between genders(EM>P/EM><0.05). Between mastoid area and the distance from the vertical segment of facial nerve canal to the posterior wall of external acoustic meatus there is inverse correlation, and the relevance has the remarkable significance. However, there was no correlation between mastoid area and the vertical segment of facial nerve canal to the rear edge of external ear. Conclusion There was some relationship between the location of the vertical segment of facial nerve canal and external acoustic meatus. Anatomic position of vertical facial nerve cancal and the posterior wall of external acoustic meatus can be showed clearly. CT and in combination with primitive axial images may provide reliable evidence for the diagnosis facial nerve dieases and the choice of ear surgery route.