Abstract： Objective To investigate precise location of sellar floor for pituitary adenoma resection through unilateral endonasal transsphenoidal approach. Method Sagittal and coronal CT scans and MRI scans were all made in 77 patients. The skull base sellar angle and sellar clivus angle were measured. The distance from anterior nasal spine to skull base sellar angle and to sellar clivus angle were measured. The shortest distance of bilateral carotid arteries was measured. After we had found the skull base sellar angle and rounded the sellar floor to find the sellar clivus angle intraoperative, the sellar floor could be confirmed. Results There were 61 patients with skull base sellar angles ≥90°, 16 patients with skull base sellar angles <90° ,48 patients with sellar clivus angles ≥90° ,29 patients with sellar clivas angles <90°. The average distance from anterior nasal spine to skull base sellar angle was (64. 90 ± 7. 41) mm. The average distancefrom anterior nasal spine to sellar clivus angle was(71.74 ±7. 70) mm. The sellar floors were all found out accurately. The pituitary adenomas were resected without severe complications. Conclusions CT and MRI scans could help to realize the shapes and positions of sellar floor and sphenoidal sinus. The two angles may be applied to localize the sellar floor for pituitary adenoma resection.