Objective Degenerative spondylolisthesis(D-SPL) and isthmic spondylolisthesis(I-SPL) are commonly seen by clinicians and require fusion surgery to be considered for sagittal spino-pelvic alignment which is poorly understood. While D-SPL and I-SPL are different in the etiopathogenesis although the overall same spondylolisthesis. Therefore,the present study was to investigate the characteristics of sagittal spino-pelvic alignment between adult degenerative and isthmic lumbar spondylolisthesis,and to explore the possible mechanism in their pathogenesis.