Abstract: Objective To evaluate the effects of magnesium sulfate on circulation fluctuation induced by the injection of pituitrin into the uterine body during laparoscopic myomectomy. Methods A total of 50 patients who were scheduled for laparoscopic myomectomy were enrolled. According to the random number table method, they were divided into two groups (n=25): a magnesium sulfate group and a control group. Then, 10 min before pituitrin injection, the magnesium sulfate group was intravenously infused with magnesium sulfate at a loading dose of 40 mg·kg^-1, followed by continuous pumping at 30 mg·kg^-1·h^-1 over 30 min. Meanwhile, 10 min before pituitrin injection, the control group was intravenously infused with the same volume of normal saline, followed by continuous pumping with the same volume of normal saline over 30 min. Their mean arterial pressure (MAP) and heart rate (HR) were collected after anesthesia induction (T1), 10 min before pituitrin injection (T2), 5 min after pituitrin injection (T3), 10 min after pituitrin injection (T4) and 20 min after pituitrin injection (T5), and after surgery (T6). Their Fromme scores, the volume of intraoperative blood loss, serum magnesium ion concentration, recovery time and extubation time were recorded. Their pain scores (NRS score) were evaluated 5 min and 20 min after extubation. Results Compared with the control group, the magnesium sulfate group presented remarkably reduced MAP and increased HR at T3-T5 (P<0.05). No difference was found in Fromme scores and the volume of intraoperative blood loss between the two groups (P>0.05). Compared with the control group, the magnesium sulfate group produced remarkable decreases in NRS scores 5 min and 20 min after extubation (P<0.05). Conclusions Pre-injection of magnesium sulfate can reduce the circulation fluctuation induced by the injection of pituitrin into the uterine body during laparoscopic myomectomy, and relieve the degree of postoperative pain, without prolonging patient recovery and extubation time.