Objectives: To study the differences between sevoflurane and isoflurane in abdomen surgery anesthetized with the target-controlled close-loop anesthesia system.Methods: Forty patients (ASA I-II) were divided into sevoflurane group (n=25) and isoflurane group (n= 15).BIS value of 55 was the control variable index.The target-controlled infusion system of sevoflurane was administered for the maintenance of anesthesia in both groups after intravenous nduction. The BIS values,blood pressures,heart rates and doses of assistant drugs were recorded and analyzed.Results: No statistical difference was observed in BIS、HR and pulse pressure in two groups. During the maintenance of anesthesia, oscillations of BIS and SBP in sevoflurane group were statistically less than those in isoflurane group (P