Abstract: Objective To evaluate the effect of magnesium sulfate on hemodynamics changes induced by intra uterus muscular pituitrin injection during laparoscopic myomectomy. Methods 50 patients who were scheduled for elective laparoscopic myomectomy were recruited and divided into Magnesium sulfate group (M group) and control group (C group) by using random number table, with 25 cases in each group. Group M received magnesium sulfate 40mg·kg-1 loading dose 10 minutes before injection of pituitrin and then received 30mg·kg-1·h-1 maintenance infusion during the next 30 min. Group C received the same volume of 0.9% saline infusion as Group M. The value of MAP and HR in both groups at the following time points: after anesthesia induction (T1), at the time of 10 min before intramuscular injection of pituitrin (T2), at the time of 5 min (T3), 10 min(T4) and 20 min (T5) after intramuscular injection of Pituitrin, and by the end of surgery(T6). The patients’ Fromme scores, the volume of intraoperative blood loss, serum magnesium ion concentration, recovery time and extubation time have been recorded either. At last, the pain scores(NRS score) was recorded 5 min and 20 min after extubation. Results Compared with the control group, the MAP of magnesium sulfate group was significantly lower at T3～T5 , while the HR of magnesium sulfate group was significantly higher（P<0.05）. The differences of patients’ Fromme scores and the volume of intraoperative blood loss have no significance between the two groups. Compared with the control group, the 5min and 20min NRS scores of the Magnesium Sulfate group were lower after extubation (P<0.05). Conclusion Pre-injection of magnesium sulfate can reduce the hemodynamic fluctuation induced by uterine body injection of vasopressin during laparoscopic myomectomy, reduce the degree of postoperative pain, and not prolong the patient’s recovery and extubation time. Therefore, the results of this study have a certain significance for improving the safety of general anesthesia in such patients.