Abstract: [Abstract] Objective:To investigate the advantages of the modified transforaminal endoscopic spine system（TESSYS）technique united interlaminar and posterolateral approach of endoscopic in treatment of degenerative spinal stenosis decompression.Methods:41 patients with degenerative spinal stenosis were decompressed by modified TESSYS technique united posterolateral approachs.The NRS scores，the ODI index and the JOA scores were evaluated before and after the operation，the sagittal diameter of the spinal canal，the space between intervertebral disc and ligamentum flavum，the area of the vertebral canal，and the anterior and posterior diameter of the intervertebral foramen.Results:The operation time was 82～114min，with an average of（91.31±10.64）min.The intraoperative bleeding was 130～210ml，with an average of（174.38±31.18）ml.1 cases with limb in the lower extremities，2 cases of cerebrospinal fluid leakage.The followup time was 12～15weeks，with the average of（13.37±2.38）weeks.There was statistical significance difference between before and after operation NRS score，ODI index，JOA score（P<0.05）.The sagittal diameter of the spinal canal，the space between intervertebral disc and ligamentum flavum，the area of the vertebral canal，and the anterior and posterior diameter of the intervertebral foramen were increased after operation 24.05%，53.99%，45.35%，21.34% separately，there was statistical significance compared with that before operation（P<0.05）.Conclusion:The combined interlaminar and transforaminal approach approachs of endoscopic could significantly expand the effective space of lumbar spinal canal and improve the clinical symptoms of patients with degenerative lumbar spinal stenosis，and without affecting the stability of lumbar.

Key words: degenerative lumbar spinal stenosis, decompression, interlaminar approach, posterolateral approach, minimally invasive