Objective To evaluate the efficacy and adverse effect of brachial plexus block with morphine and ropivacaine for postoperative analgesia in children. Methods Forty-five children undergone upper extremity surgery were randomly divided into three groups (n = 15) , ie, Croup A (brachial plexus block with ropivacaine), Croup B (brachial plexus block with ropivacaine and subcutaneous injection of morphine) and Croup C (brachial plexus block with morphine and ropivacaine). The analgesic effect and the analgesia maintenance time were recorded by FLACC method at 1, 2, 4, 6, 8, 12, 24 hours after operation. The adverse reactions were observed 48 hours after operation. Results There was no statistical difference between Croup A and Croup B in the analgesia maintenance time and the number of cases without analgesic therapy at each time point (P > 0. 05). Compared with Croup A or Croup B, the analgesia maintenance time in Croup C were significantly extended and the number of cases without analgesic therapy at 4, 6, 8, 12, 24 hours after operation were significantly increased (P < 0.05). The adverse effect was fairly light in three groups. Conclusion Brachial plexus block with morphine and ropivacaine may extend analgesia maintenance time effectively and safely in children undergone upper extremity surgery.