Objective: To investigate the efficacy and safety of combined spinal-epidural (CSE) anesthesia using a 25G spinal fine needle via a single puncture for lower limb surgery in children. Methods: Sixty pediatric patients scheduled for surgery were randomly divided into two groups, with 30 patients in each. The control group received subarachnoid anesthesia with 2–2.5 mL of 0.33% ropivacaine. The experimental group received the same ropivacaine dose, followed by withdrawal of the needle to the epidural space and administration of 0.1 mg hydromorphone diluted to 5 mL. The anesthetic and analgesic effects, incidence of complications, and postoperative family satisfaction were observed in both groups. Results: Compared with the control group, the experimental group showed a higher anesthesia success rate, a shorter onset time, and a longer maintenance time of anesthesia (p < 0.05). Postoperative analgesia at various time points was significantly better in the experimental group (p < 0.05). The total incidence of complications was lower in the experimental group, though the difference was not statistically significant (p > 0.05). Family satisfaction was significantly higher in the experimental group (p < 0.05). Conclusion: CSE anesthesia using a 25G fine needle via a single puncture for pediatric lower limb surgery is safe and effective. It can significantly improve surgical outcomes and is worthy of clinical promotion.