To understand the blomechanical behavior of lumbar spine after removal of nucleus pulposus (NP)and resection of posterlor structure(PS) by means of measurement of stiffness in compression, shear and torsion, and torsion strength. Materials and Methodst twenty-four FSUs made from eight adult fresh cadaver spine (L1-S1) were divided into three groups randomly. Two groups were removed of NP and PS respectively, and one group was chosen as a control. Each specimen were loaded in compression and shearing, then rotated to rupture. The stiffness of compression, shear and torsion of lumbar FSU were decreased after removal of NP or PS, as well as the torsion strength. The stiffness of shear in left/right and torsion decreased significantly(p<0.05), and the torsion strength decreased sign1ficantly(p<0.01) following removal of NP. After resection of PS, the stiffness of shear in left/right and torsion reduced significantly(p<0.05), and the stiffness of compression and shear in anterioposterlor and torsion strength decreased very significant1y(p<0.01).