Objective To investigate the effectiveness of utilizing segmental decompression combined with corrective short-segment fusion surgery in the treatment of degenerative lumbar scoliosis. Methods A total of 124 cases of degenerative lumbar scoliosis patients admitted to the Second People's Hospital of Fuyang City from February 2018 to February 2023 were selected. They were randomly divided into the short-segment fusion group and the long-segment fusion group using a random number table method, with 62 cases in each group. The short-segment fusion group underwent posterior short-segment decompression and fusion, with an average fused segment of adjacent lumbar vertebrae (2.36±0.75 segments). The long-segment fusion group underwent posterior long-segment decompression and fusion, with an average fused segment of multiple adjacent lumbar vertebrae (5.42±1.40 segments). The surgical time and intraoperative blood loss were recorded. At 6 months postoperatively, the coronal Cobb angle of lumbar convexity, sagittal Cobb angle of lumbar lordosis, intervertebral foramen height, intervertebral space height, intervertebral foramen area, spinal canal area, spinal canal diameter, Japanese Orthopedic Association score (JOA), Oswestry Disability Index (ODI), degree of pain in the lumbar and lower extremities, serum tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) levels, as well as postoperative complications were compared between the two groups. Results The intraoperative blood loss and surgical time in the short-segment fusion group were both lower than those in the long-segment fusion group (P＜0.05). At 6 months postoperatively, the coronal Cobb angle of lumbar convexity decreased and the sagittal Cobb angle of lumbar lordosis increased compared to preoperative measurements in both groups (P＜0.05), but there was no significant difference between the two groups (P＞0.05). At 6 months post-surgery, the intervertebral foramen height, intervertebral space height, intervertebral foramen area, spinal canal area, and spinal canal diameter all showed an increase in both groups of patients. The short segment fusion group exhibited higher measurements compared to the long segment fusion group (P<0.05). At 6 months postoperatively, the JOA scores of both groups improved compared to preoperative scores, with the short-segment fusion group showing higher improvement than the long-segment fusion group (P＜0.05); the ODI scores of both groups decreased compared to preoperative scores, with the short-segment fusion group showing greater improvement than the long-segment fusion group (P＜0.05). At 6 months postoperatively, the pain scores in the lumbar and lower extremities, as well as the levels of TNF-α and IL-1β, decreased compared to preoperative levels in both groups (P＜0.05), with no significant difference between the two groups (P＞0.05). In the long-segment fusion group, two cases experienced dural tearing during the decompression process due to adhesions between the lamina and dura mater, while no severe complications were observed in the short-segment fusion group. Conclusion Both short-segment decompression fixation fusion and long-segment decompression fixation fusion through a posterior approach can achieve good therapeutic effects in the treatment of degenerative lumbar scoliosis. However, compared to the long-segment fusion group, the short-segment fusion group undergoing short-segment decompression fixation fusion through a posterior approach has a shorter surgical time, lower intraoperative blood loss, better recovery of lumbar function, and lower risk of postoperative complications.