In this study, we evaluated the efficacy and safety of 1μg/kg dexmedetomidine as an adjuvant treatment to ropivacaine in children undergoing upper limb surgeries under ultrasound-guided axillary brachial plexus blocks and general anesthesia. We enrolled 90 children (aged 1-8years; ASA I-II) undergoing closed reduction and internal fixation for upper extremity fractures at the Xiamen Children's Hospital and randomly assigned them to one of two groups: L (injection with 0.25% ropivacaine) or D (injection with 0.25% ropivacaine containing 1μg/kg dexmedetomidine) using the random number table method. The main outcome indicators recorded were the facial expression, leg activity, position, crying, and Face, Legs, Activity, Cry, and Consolability (FLACC) scale scores of children after surgery and the duration of block and analgesia maintenance. The secondary outcome indicators were vital sign data at the time of ultrasound probe placement (T1), at the time of block completion (T2), prior to the beginning of surgery (T3), 5min after the beginning of surgery (T4), and at the end of surgery (T5), as well as the time of postoperative recovery, the number of cases of remedial analgesia, and complications. There was no statistical difference between the two groups in terms of general data, block completion time, postoperative recovery time, and complications (P > 0.05). Compared to the L group, the D group had significantly lower FLACC scores at 6h after surgery, as well as significantly lower systolic blood pressure, diastolic blood pressure, and heart rate values at T4 and T5, and significantly longer duration of postoperative analgesia maintenance (all P < 0.05). Dexmedetomidine (1μg/kg) as a local anesthetic adjuvant to ropivacaine can alleviate pain at 6h postoperatively, prolong analgesia maintenance, and reduce intraoperative blood pressure and heart rate in pediatric patients undergoing closed reduction and internal fixation for upper extremity fractures, with no obvious complications or delayed recovery. Registration website: www.chictr.org.cn, Registration number: ChiCTR2200065163, Registration date: October, 30, 2022.