Objective Evaluation the effect of intraoperative intravenous magnesium sulfate on propofol , fentanyl dose and postoperative adverse events. Methods Sixty ASA I orⅡ patients of either sex，aged18-60 yrs.，undergoing craniocerebral surgery with general anesthesia were randomly divided into 2 groups(n=30 each)：control group(group C)and magnesium sulfate group(group T)．T group received intravenous 50 mg/kg magnesium sulfate after the induction, while C group received normal saline. Blood concentration of magnesium was measured before and after operation. The dose of intraoperative propofol and fentanyl, and the incidence of postoperative pain, nausea and vomiting, muscle tension and tendon reflex and other adverse events at different time were recorded. Results Intraoperative intravenous magnesium sulfate can effectively reduce the intraoperative propofol and fentanyl dosage（P<0.05）, and alleviate postoperation pain（P<0.05）. While, there was no obvious change in adverse events, such as Nausea and vomiting, muscle tension and tendon reflex, and postoperative blood concentration of magnesium（P>0.05）. Conclusion Intraoperative intravenous magnesium sulfate (50 mg/kg) can effectively reduce the intraoperative propofol and fentanyl dosage, and can effectively alleviate postoperative pain, while had no obvious effect on postoperative adverse events.