Objective To explore the feasibility of surgical volume index (SPI) in predicting postoperative pain in children undergoing adenotonsillectomy under general anesthesia. Methods A total of 120 children aged 4 to 8 years, boys or girls, the American Society of Anesthesiologists (ASA) grades Ⅰ or Ⅱ, who were scheduled for elective adenotonsillectomy under general anesthesia were selected. Non‑invasive blood pressure, electrocardiogram, pulse oxygen saturation (SpO2), and SPI were monitored after the children entered the operating room. All patients received tracheal intubation for general anesthesia, and SPI was maintained between 20 and 50 during the surgery. Five minute before the end of the surgery, the infusion of anesthetics was stopped. The average arterial pressure (MAP), heart rate (HR), and SPI were recorded immediately at the end of surgery and at post‑operation 1, 2, 3, 4 min and 5 min, with the maximum values defined as MAPmax, HRmax, and SPImax, respectively. After extubation, rgw patients were transferred to the post‑anesthesia care unit (PACU) for continued observation. Pain was assessed using the modified Children's Hospital of Eastern Ontario Pain Scale (m‑CHEOPS) at 10, 20 min and 30 min in PACU, and the maximum scores were analyzed. Based on the occurrence of moderate to severe pain, receiver operating characteristic (ROC) curves were plotted for MAPmax, HRmax, and SPImax. Results The trial was completed in 112 children. Within 30 min after entering PACU, 89 children (79.5%) had no pain or mild pain, 18 (16.1%) experienced moderate pain, and 5 (4.4%) experienced severe pain. The ROC curves showed that the area under the curve (AUC) for SPImax was 0.83, with a sensitivity of 78.8% and specificity of 86.8%, indicating good predictive efficiency for moderate to severe pain; the optimal cutoff value for SPI was 44.5. In contrast, the AUC for MAPmax and HRmax was 0.55 and 0.61, respectively, indicating that neither could predict the occurrence of moderate to severe pain postoperatively. Conclusion SPI can effectively predict the early occurrence of moderate to severe pain in children following adenotonsillectomy under general anesthesia.