The third ventricle is a narrow, funnel-shaped, unilocular, midline cavity located between the 2 thalami, under the body of the lateral ventricle, in the center of the head. Damaging of brain tissue in the third ventricle when conducting operation under the microscope will lead to serious consequence. The study aimed to precisely detect the relative location of specific structures on the approach to the third ventricle. The authors rebuilt a 3-dimensional reconstruction of the brain and selected specific sections and then measured several crucial distance, angle to precisely assure the approaching pathway and localize the hypothalamic sulcus, interthalamic adhesion, anterior commissure, optic chiasm, and pineal body. In the study, canthomeatal line was used as base line to measure angle. Parameters were obtained from 58 samples (22 males and 36 females) between 21 and 76 years old. Means and standard deviation were calculated as well as the 95% confidence interval for the mean value of the measured data. The data were analyzed by SPSS, statistical software with the comparison between sexes and sides. The results could be reference for clinical and anatomic utilities.