【Abstract】 Objective To identify the effect of dexmedetomidine added to ropivacaine on ultrasoundguided transversus abdominis plane block for postoperative analgesia after cesarean section. Methods 100 parturient women underwent cesarean sections from August 2016 to January 2017 were randomly divided into group D and group C. Bilateral TAPB was completed with totally 60ml 025% ropivacaine and 1ug/kg dexmedetomidine for group D and only totally 60ml 025% ropivacaine for group C. Patient—controlled IV analgesic(PCIA) pumps were started at the end of surgery. Time elapsed for the first additional analgesia request was recorded and VAS and BCS score, frequency of PCIA pressed at 4, 8, 12, 24 and 48 h after operation and adverse reaction were also compared. Results Patients in both groups had no TAPBrelated complication. The time elapsed for the first additional analgesia request in group D were significantly higher than that in group C（P＜005）. Compared with group C, VAS score were significantly low and BCS score was significantly high at postoperative 8, 12, 24h（P＜005）. The frequency of PCIA pressed in group C were significantly lower than that in group D at 48h, 812h, 1224h, 2448h time intervals (P＜005). Conclusion Adding 1ug/kg dexmedetomidine to 025% ropivacaine in TAPB potentiats the analgesic properties of ropivacaine, reduces sufentanil consumption and safely provides good pain control after cesarean section.