Using biomechanical experimental technics, Was analysed Cause of disease mechanism ofbiomechanim for unstable pelvic fracture, 6 specimens of human pelvic taken from fresh cadavers ofbrain injure after sudden death wasused in this study. To approach the biomechanical properties ofpelvis in normal Chinese adult, After appropriate management of the specimen, the loads in thesimulated test (stand position, side compression position,the ins and outs position) are 500N, 1000N.With strain electric measuring apparatus, the distribution of main stress and main strain, and theirdirection angles, ultimate load and shape of unstable pelvic were acquired. So the type of pelvicfracture and cause of disease mechanism for unstable pelvic fracture should be very complicated.Biomechanical parameters were provided the theoretical in c1inical application of differentinterfixation for vertically unstable pelvic fracture.