To investigate the stress changes of lumbar vertebrae internal structure in torsion by using a finite element mod-el.The three-dimensional finite element model of an intact L 4 -L 5 lumbar motion segment was established and loaded under different force of torsion.The results showed that the rotation degrees of L 4 -L 5 segment,average axial effective stress of intervertebral disc,pore pressure,fiber stress and strain and facet load increased with the increase of torsion.