Abstract： Objective： To observe the effects of quadriaxial three-directional reduction combined with modified splint fixation on swelling/pain severity and elbow anatomical structure relationships in children with supracondylar humeral fractures. Methods： A retrospective analysis was performed on the clinical data of 90 children with supracondylar humeral fractures treated at Zhongshan Chenxinghai Hospital of Integrated Traditional Chinese and Western Medicine from May 2022 to November 2024. They were divided into the control group and the observation group based on different treatment protocols，with 45 cases in each group. The control group received manual reduction with minimally invasive pinning and plaster fixation， while the observation group underwent quadriaxial three-directional reduction with modified splint fixation. The postoperative hospitalization time and fracture healing time，the degree of swelling and pain at the fracture site， the relationship between the anatomical structure of the elbow， imaging parameters，Mayo Elbow Performance Score（ MEPS），the excellent and good rate，and the incidence of complications were compared between the two groups. Results：After treatment，the fracture healing time and postoperative hospital stay in the observation group were significantly shorter than those in the control group （P＜0.05）. On postoperative day 1，there was no statistically significant difference in swelling degree or VAS scores for pain between the two groups （P＞ 0.05）. On postoperative days 3，7，and 14，both groups showed a trend of initial increase followed by a decrease in swelling degree and VAS scores for pain. By postoperative day 14，swelling degree in both groups decreased compared to day 1，and it was significantly lower in the observation group than in the control group （P＜0.05）. The VAS scores in the observation group were significantly lower than those on postoperative day 1 and also significantly lower than those in the control group （P＜0.05）. There were no statistically significant differences in the imaging parameters of capitulum humeri anteversion and Baumann angle between the two groups at 1 day，3 months，and 6 months postoperatively（ P＞ 0.05）. At 1 month postoperatively，there was no significant difference in flexion angle and carrying angle between the groups （P＞0.05）. At 3 and 6 months postoperatively， both angles showed an increasing trend and were significantly greater than those at 1 month postoperatively （P＜0.05）. Furthermore，the observation group had significantly greater flexion and carrying angles than the control group at the same time points （P＜0.05）. At 12 months postoperatively，the MEPS score in the observation group was 91.47 ± 4.13， significantly higher than that of 85.63 ± 3.78 in the control group （P＜0.05）. The excellent and good rate for elbow function was 91.11% （41/45） in the observation group， significantly higher than that of 73.33% （33/45） in the control group （P＜0.05）. No complications such as vascular nerve injury， infection， or varus deformity occurred in either group. Conclusion： For children with supracondylar humeral fractures，the quadriaxial three-directional reduction combined with modified splint fixation can significantly reduce swelling and pain at the fracture site，improve the anatomical structure relationships of the elbow，promote the recovery of elbow function，and shorten the rehabilitation process.