Previous studies have shown that the incidence of postoperative stroke, particularly covert stroke, is high following brain tumor resection and is closely associated with inflammatory responses and disruption of the blood-brain barrier. Ulinastatin, a broad-spectrum protease inhibitor, exerts multiple pharmacological effects including anti-inflammatory activity and protection of the blood-brain barrier; however, its efficacy in preventing postoperative stroke has not been validated by prospective studies. Therefore, a single-center, randomized, double-blind, placebo-controlled trial will be conducted, enrolling 1,370 patients undergoing elective supratentorial tumor resection. Patients will receive ulinastatin (6,000 IU/kg) or normal saline both before and after surgery. This study aims to evaluate whether ulinastatin reduces the incidence of postoperative stroke, thereby providing high-level evidence for perioperative brain protection in patients undergoing brain tumor surgery.