Objective:To analyze whether supraspinal ligamen can be the identification marker of the sagital srew angle(SSA) of the pedicle of vertebral arch in the thoracolumbar surgery. Methods:Total of 63 cases of the nomal thoracolumbar MRI and 20 cases of fracture thoracolumbar MRI of patients were included in the study. Supraspinal ligament with the theoretical angle of pedicle of vertebral arch nail was measured and analyzed. The correlation was analyzed between SSA of the pedicle of vertebral arch at the thoracic vertebral 10(T10) and lumbar vertebrae 4(L4) and the supraspinal ligament.. Results:The angle of terminal plate of vertebral body agianst supraspinal ligamen is 90°at T10-L3, and is about 82°at L4,which is nearly to 90°. The angle didn＇t change before and after thoracolumbar fracture. Conclusion:If the angle of terminal plate of vertebral body agianst supraspinal ligamen is about 90° at T10-L4,the SSA is 0°. In the internal fixation surgery of thoracolumbar fracture, supraspinal ligament can be the identification marker for SSA of the pedicle of vertebral arch in the operation.