Objective: in order to improve the effect of the spinal reduction and fixation, let fixation devicesare good enough to conform the biomechanical requirement. Mathods: The experiment was carriedout with 7 human cadaver thoracolumbar spinal specimens. Models of unable thoraco lumberfracfures were caused by artificial stress on these specimens and new spinal fixation devices wereused in these specimens. The stress(stain), displacement, strength, rigidity and stabilization on thelumbar spinal specimens were measured with four different physiological conditions. Rusultf Theresult of the biomechanical tests on this device showed that MF was better than Dick and Steffee inall of strength, anti-axial compression, anti-rotation, rigidity and stability(p<0.01). Conclusion f Theresults of this spinal fixation instrument in treatment of 21 cases of unstable thoracolumbarfractures were statisfactory. This study indicated that this device is worth for application andpopularizing.