Objective To compare the clinical effects of different concentrations of low volumn of ropivacaine during MED. Methods 150 patients performed MED were randomly divided into three groups: in the first group (n=50) 0.8% ropivacaine was used, in the second group (n=61) 0.6% Ropivacaine was used and in the third group 0.4% Ropivacaine was used. First epidural needle was introduced into the epidural space. Then edpidual catheter was introduced into the epidural space and 5ml of 2% lidocaine was injected. After anesthesia planum was obtained, 5ml of ropivacained in different concentrations was iniected through the epidural catheter in different groups. The react time, the resume time and the separate anaesthesia among three groups were compared Results The blockade of sensory nerve was faster than that of motor nerve, and persistent time of sensory nerve was longer than that of motor nerve. Group two had more remarkable separate sensory and motor blockade than group one and group three (P