Abstract: To investigate the biomechanic characteristics of human lumbar spine, a three-dimensional finite element model was developed for the spine segment T12-S1 to describe in details both of external configuration and internal components as well as all kinds of ligaments so as to show the real human spine as exact as possible. The analytical results indicated that the resonant frequency of the vertebra T12-S1 is 7.68 Hz in vertical direction. Both intervertebral denucleation and removal of facets and their capsular ligaments may decrease the resonant frequencies to different degrees, but the influence of the denucleation exerts on the frequencies much greater than that due to the removal. It was shown that the dynamic characteristics of the T12-S1 model comply with the actuality of human spine, so available to the relevant studies.