Objective To observe the biomechanical effects of an interspinous stabilization system (Wallis) on the behavior of a vertebral segment. Methods Six fresh adult human cadaveric lumbar spine specimens (L1-S1) were divided into experiment group, injured group, positive control group and intact group. The intact group was complete specimens, the positive control group was implanted with pedicle screw, while the experiment group was implanted with Wallis system. Before-after controllde study was used. In four groups, the range of motion of lumbar spine and the stress changes in a vertebral segment under flexion extension, lateral bending and axial rotion were examined. Statistical analysis of the data was done. Results The effect of the implant appeared: experimental results showed reduced range of filexionextension motion of the instrumented spine regarding the injured and intact one, and but no difference of lateral bending and axial rotion motion with the injured, but increased than intact and control group Significantly. A decrease of stresses in the disc and zygapophysial joints that of the fixed segments and adjacent segments. The stresses of experiment group in the disc and that of the adjacent segments have a difference reduce with positive control group. Conclusion Wallis system appeared to reduce motion without suppressing it and to lower stress in the disc fibers and zygapophysial joints, and reduce the stress concentration of adjacent segments. Key words: Lumbar spine; Interspinous instrumentation; Biomechanics