Abstract: ob＜x＞jective: To explore the risk factors of Intraoperative cerebrospinal fluid leakage and repair strategy of skull ba＜x＞se defects during neuroendoscopic transnasal pituitary tumor resection . Methods: We conducted a retrospective review of 186 patients with pituitary adenoma between January 2018 to December 2019, in ** ,who underwent endoscopic endonasal transsphenoidal surgeries .The clinical data were analyzed, and the correlation between the size, type, texture, invasivity, degree of resection,secondary operation of pituitary tumor and intraoperative cerebrospinal fluid leakage was compared. The risk factors of intraoperative cerebrospinal fluid leakage were discussed through multivariate statistical analysis.According to the classification of cerebrospinal fluid leakage during operation, the corresponding repair strategy of skull ba＜x＞se was adopted.Results：Of 186 patients ,there were 34(18.3%)patients with intraoperative cerebrospinal fluid leakage.The incidence of intraoperative cerebrospinal fluid leakage was correlated with tumor size, secondary operation, and tumor texture, and they were independent risk factors for intraoperative cerebrospinal fluid leakage. However, the type of pituitary tumor, Knosp grade, and surgical resection degree were not clearly correlated with the occurrence of intraoperative cerebrospinal fluid rhinorrhea, and the results were not statistically significant.Among the 34 patients with intraoperative cerebrospinal fluid leakage, 18 cases were grade 1, 10 cases were grade 2, and 6 cases were grade 3. There were 6 cases of postoperative cerebrospinal fluid rhinorrhea, 5 cases were cured by conservative treatment, and only 1 case was repaired by skull ba＜x＞se reconstruction . No recurrent cerebrospinal fluid rhinorrhea was observed during postoperative follow-up of 3 months to 1 year.Conclusion The occurrence of cerebrospinal fluid leakage during endoscopic transpituitary tumor resection is closely related to tumor size, secondary operation and tumor texture.Once cerebrospinal fluid leakage occurs during the operation,graded skull ba＜x＞se repair is safe and effective