Objective To investigate the effect from sequential removal of posterior ligamentous complex (PLC) on stability of injured thoracolumbar spine, and verify the role of supraspinous ligaments in maintaining stability of injured thoracolumbar spine complex. Methods Eight fresh human thoracolumbar specimens (T11-L3) were selected, and 1/3 of the L1 vertebral body was resected for "V" shape. The specimens were then mounted on the universal testing machine and subjected flexion and compression to make a fracture in L1. PLC in T12-L1 segment was then resected in a sequential manner from facet capsular ligament (FCL), interspinous ligament (ISL), supraspinous ligament (SSL) to ligamentum flavum (LF). The range of motion (ROM) and neutral zone (NZ) of the T12-L1 segment under flexion, extension, lateral bending and rotation movement were measured at each ligament removal step. Results Under flexion and extension, ROM and NZ presented a significant increase after fracture and removal of SSL. Under right lateral bending, ROM increased sharply after reduction of vertebrae and FCL, while the NZ showed a slight increase. Under left axial rotation, removal of vertebrae and FCL resulted in a significant increase in ROM, while the NZ showed no significant increase. Conclusions After removal of SSL, the stability of the T12-L1 segment decreases sharply, especially under flexion motion, and SSL is the pivotal ligament for PLC to maintain the stability of thoracolumbar spine.