Objective: To evaluate the efficacy of ultrasound-guided caudal epidural block for postoperative analgesia in the infants undergoing lobectomy under general anesthesia. Methods: Sixty American Society of Anesthesiology physical status Ⅱ or Ⅲ pediatric patients of both sexes, aged 1-3 yr, weighing 10-16 kg, scheduled for elective lobectomy under general anesthesia, were divided into 2 groups (n=30 each) using a random number table method: control group (group C) and epidural block group (group E). Caudal epidural block was performed under ultrasound guidance after induction of general anesthesia and at 15 min before surgery in group E. An epidural catheter was inserted at T_{6, 7} interspace, 0.1% ropivacaine 1 mg/kg was injected at 5 min after injecting 1% lidocaine 3 ml, the diffusion of epidural fluid was controlled at T_3-10, and the epidural catheter was then removed.An analgesia pump was connected at the end of the surgery in two groups.Pain was evaluated using Face Legs Activity Cry Consolability scale.When Face Legs Activity Cry Consolability scale score>3, the pump was pressed.When pain was still unrelieved 5 min later, sufentanil 0.1-0.2 μg/kg was intravenously injected.The patients were followed up for 48 h after operation, and the requirement for additional remifentanil and sufentanil, and the occurrence of postoperative nausea and vomiting, respiratory depression, hypoxemia and over-sedation was recorded.The number of pressing times, extubation time and duration of intensive care unit stay were also recorded.Pain at 1 and 2 days after operation was evaluated using the Postoperative Pain Measure for Parents. Results: Compared with group C, the consumption of remifentanil, the number of pressing times and requirement for additional sufentanil were significantly decreased, the incidence of each index of the Postoperative Pain Masure for Patients was decreased at 1 day after surgery, the extubation time and duration of intensive care unit stay were shortened, and the incidence of nausea and vomiting and over-sedation was decreased in group E (P<0.05). Conclusion Ultrasound-guided caudal epidural block provides better efficacy and fewer side effects for postoperative analgesia in the infants undergoing lobectomy under general anesthesia.