1. Clinical data 17 patients with giant pituitary adenoma in this group, 8 males and 9 females, aged 35-67 years. The clinical manifestations were headache, vision loss, etc.; the maximum diameter of the tumor was 4.2 cm to 6.2 cm; 2. The anterior inferior wall of the pterygoid sinus is exposed, the opening of the pterygoid sinus is enlarged with a grinding drill, the septum of the pterygoid sinus is removed, the internal carotid artery bulge on both sides of the pterygoid sinus is identified and exposed, the saddle base is completely exposed, the saddle base is opened with a grinding drill, the scope of the saddle base opening is decided according to the size of the tumor, some of the giant adenomas can be enlarged and part of the pterygoid plateau is removed according to the scope of the tumor. When the tumor cavity is large enough, the endoscope can enter the intra-, supra- and even intra-three-ventricular ventricles, and remove the residual tumor under the direct view of the endoscope, and try to gently remove the tumor with the suction device and avoid scraping with the spoon to protect the residual pituitary tissue. After resection, the tumor cavity was directly connected with the three ventricles and lateral ventricles, and the intracerebroventricular cavity was avoided to be filled with hemostatic materials. 3. Results: Among the 17 patients, 12 patients had total resection and 5 patients had subtotal resection, and all of them had different degrees of improvement in their postoperative symptoms and vision loss. All of them had different degrees of transient increase in urine volume after surgery, which improved after giving posterior pituitary hormone treatment, and all of them reached normal urine volume at the time of discharge. There was no nasal leakage of cerebral crest fluid or intracranial infection. Two cases had a small amount of postoperative blood leakage from the tumor cavity, which did not cause obvious clinical symptoms, and the review before discharge showed that the bleeding was absorbed. 4. Discussion: Neuroendoscopic transsphenoidal approach to remove pituitary tumor is an ideal procedure to remove pituitary tumor because of its good exposure of the saddle area structure, high rate of total tumor resection, small surgical trauma, few complications and fast recovery of patients after surgery. Compared with the traditional transnasal butterfly surgery, this procedure also has the shortcomings of limited operating space, inconvenient use of microscopic instruments and easy contamination of endoscopic lens, which requires the operator to have solid knowledge of endoscopic anatomy and skillful surgical skills. Only on the premise of mastering the anatomy and operation techniques of transnasal butterfly approach can the advantages of neuroendoscopy in transnasal butterfly surgery be fully utilized to achieve satisfactory results of minimally invasive surgery. For the operation of huge pituitary adenoma protruding into the three ventricles in this group, we have the following experiences: (1) Although the tumor is huge and protrudes into the three ventricles, it is not very invasive and generally the wall of cavernous sinus is relatively intact, so it is easy to be completely removed. (2) Pituitary tumors that easily invade into the three ventricles are generally soft in texture and can be easily removed by suction gradually, so they are easier to be removed. (3) Although the tumor invades into the three ventricles, the adhesion with the wall of the three ventricles is generally light, so the wall of the three ventricles will not be damaged during resection. (4) Preoperative drainage by lumbar puncture can reduce the difficulty of surgery caused by premature descent of the saddle septum, or after cutting open the saddle septum and releasing part of the cerebral crest fluid, it can facilitate further resection of the tumor that breaks through the saddle septal foramen and develops upward. (5) Since the operative cavity communicates directly with the ventricle, the chance of postoperative cerebral crest fluid leakage is higher, and it is necessary to carefully repair the saddle base in layers intraoperatively, and the tipped nasal septum mucosal flap is an important skull base repair material.