Objective To construct 3D finite element model of the thoracolumbar spinal cord, and study the mechanism of spinal cord injury caused by burst fracture through biomechanical experiments. Methods The compression simulation on burst fracture was performed using finite element technology, and the results were verified by comparing the tested models with the in vivo and in vitro experimental results. Results The strain distribution in white matter of the spinal cord was higher than that in grey matter at the initial stage of burst fracture. As the displacement of bony fragments increased, the strain distribution in grey matter increased subsequently. But when the displacement of bony fragments finally reached the maximum, the strain in white matter was higher than that in grey matter. Conclusions Traumatic severity of the spinal cord during burst fracture is dependent on the posterior encroachment, and the traumatic procedure order for ventral horn (motor function) or dorsal horn (sensory function) of cord tissue also plays an important role in the evaluation. In clinical practice, the patient’s condition can be evaluated more accurately by assessing severity of the spinal motor and sensory functions. Further understanding on strain distribution in the spinal cord during the injury may inspire new strategies for treating or preventing spinal cord injury.