Abstract: Objective: To observe the influence of epidural anesthesia on heart rate variability(HRV).Methods: Twenty-five ASA ⅠtoⅡ patients scheduled for elective surgery under epidural anesthesia were included in this study.They were divided into two groups according to the segment of epidural block.Group A included 15 patients undergoing cholecystectomy or gastrectomy under epidural anesthesia on middle chest segment and group B included 10 patients undergoing orthopaedics operation on lower limbs under epidural anesthesia on lumbar segment.The Power spectrum of HRV,heart rate and blood pressure(BP) were observed before and after epidural anesthesia.Results: The value of low frequency(LF) and BP were markedly reduced 5,10,15 and 20 minutes after epidural anesthesia on middle chest segment(P<0.05).The value of LF correlated closely with BP(r=0.980 2, P<0.01).HRV changed little after epidural anesthesia on lumbar segment.Conclusions: The epidural anesthesia on middle chest segment has influence on HRV and reduces the value of LF reflecting the tension of the sympathetic nerve,which correlates with the level of epidural block.