Objective To explore the biomechanical properties of locking compression plate for treating unstable sacral fractures and therefore to provide scientific foundation for clinic application.Methods 3-dimension finite element models were used to simulate normal pelvis and the unstable pelvis sufferedⅠsection ,Ⅱsection orⅢsection sacral fracture respectively and the fractures of pubis limbs.The unstable pelvises fixed with one screw for the fracture superior pubis limb and sacral screws,sacral bars or locking compression plate for the fracture of sacrum respectively were simulated.The mobility of the sacrum and pubis were calculated after giving 500N axial load on 5thlumbar vertebra and the bone stress distribution of the fixed unstable pelvis under axial load were compared with that of normal pelvis. Results Among the three fixing methods,the fixative effects of sacral screws are excellent and the effects of sacral bars and locking compression plate were similar.When the pelvis was under axial load ,the bone stress distribution of the unstable pelvis fixed with one of three methods were similar as that of normal pelvis.Conclusion It was a practical methods for treatment of the unstable sacral fractures fixed with locking compression plate,especially for the treatment of unstable sacral fractures,concomitant fracture of lilac ala or comminutedⅡsection orⅢsection sacral fracture.