Abstract: Objective To explore the clinical value of preoperative magnetic resonance imaging data measurement and tumor constitution evaluation for guiding application and protection of pituitary function in transsphenoidal pituitary adenoma resection. Methods The clinical data of 80 patients with pituitary tumor who underwent transsphenoidal pituitary adenoma resection from January 2017 to September 2019 in the First Affiliated Hospital of USTC were retrospectively analyzed. MRI imaging and pituitary hormone levels were detected before and after surgery. Results In 80 patients, the distance between the nasal columella and the midpoint of the anterior sellar floor was (71.32±2.04) mm in the sagittal position, the angle between the above measurement line and the nasal floor plane was (31.24±5.8)°, and the distance between the cavernous sinus segment of the superior internal carotid artery was (20.74±0.48) mm in the coronal position. Soft texture showed high signal intensity, while neutral texture showed low signal intensity, which was obviously enhanced after enhanced scanning. Applying the measured values to the operation, all patients successfully reached the sellar floor to remove the mass. Postoperative MRI revealed total resection in 63 cases, subtotal resection in 13 cases and partial resection in 4 cases. Conclusion The application of MRI before transsphenoidal pituitary adenoma resection can help to accurately locate, safely and maximize open sellar floor bone, and clarify texture and size of pituitary tumors. It helps the surgeon to completely remove the tumor and reduce the damage to the normal pituitary function, so that the patients' hormone can return to normal levels. This would be helpful for the future clinical application.