Objective：To evaluate the effect of carbon dioxide pneumoperitoneum on neuromuscular blockade of rocuronium in patients undergoing laparoscopic surgery. Methods：Sixty patients sche-duled for either laparoscopic or open hysterectomy procedures under general anesthesia were enrolled，30 patients in each group. The same anesthetic protocol was performed to all pa－tients. The responses of adductor pollicis to train of four（TOF） stimulation of ulnar nerve were monitored. After intubation，each patient received rocuronium by continuous infusion with initial rate of 6 μg/（kg?min） to maintain the ratio of T1 and Tc（T1/Tc） at the level between 0% and 10%. The time interval from the end of rocuronium infusion to 25% recovery of T1/Tc（T1/Tc 25%），recovery in－dex（T1/Tc from 25% to 75%），the duration of TOF from 0％ to 90%（TOF90%），dosages of rocuronium administered during anesthesia maintenance were recorded. Results：The demographic data including age，weight，height，body mass index（BMI），surgical time，dura－tion of rocuronium infusion were comparable between the groups. T1/Tc 25%，recovery index and TOF90% were significantly longer in patients underwent laparoscopic hysterectomy than in those underwent open hysterectomy（P<0.01）. The amount of rocuronium used anesthesia maintenance was less in laparoscopic group than in open group（P=0.001）. Conclusion：Carbon dioxide pneumoperitoneum appears to slow down the metabolism of recoronium，which may result in prolonged duration of action，as well as delayed recovery after muscle relaxant administration in laparoscopic surgery.