Objective　To perform the biomechanical evaluation of Coflex system by comparing the ranges of intervertebral motion and intervertebral disc stress among dynamic fixation adopting Coflex, decompression by fenestration or pedicle screw system respectively.　Methods　Three-dimensional finite element model of normal adult's lumbosacral vertebrae was established, as well the models of decompression by fenestration, dynamic fixation with Coflex and fixation with pedicle screw system separately. 500N preload and 7.5 Nm bending moment were performed on the models, while, the range of motion (ROM) and intervertebral disc stress (IDS) were measured.　Results　The ROM and IDS of Coflex model were recorded respectively as follows: on the surgical segment (L4/5), flexion (FLE) 3.15, 2.571MPa and extension(EXT) 1.21°, 2.109MPa. On the upper adjacent segment (L3/4): FLE 3.46°, 2.001MPa and EXT 2.75°,3.149MPa. On the lower adjacent segment (L5S1), FLE 3.22°, 2.681MPa and EXT 2.46°, 3.812 MP respectively.　Conclusions　Dynamic fixation with Coflex could keep some ROM and reduce IDS on the surgical segment, and has no significant effects on ROM and IDS of the adjacent segments.