Two types of accurate 3D finite element models were developed for lumbar spine L5 and L3-L5, and a series of computational analyses were carried out to identify the mechanical behavior of lumbar spine under compressive loads. In order to establish a precise FE model for single and segmental lumbar vertebrae, a group of computed tomography images was converted into a 3D geometric surface, and a tetrahedral mesh using the image processing software. For the FE analysis, two types of bones, namely, a fully filled type with cortical bone, and a cortical bone with a cancellous bone core, was considered for the investigation of the effects of the existence of central core of bone. The computational results for L5 indicate that a larger von Mises stress distribution was found on the pedicles and on the vertebral body with respect to the remaining vertebral parts. In particular, the highest equivalent stress was occurred on the surface of cortical bone in the case of a mixture of cortical and cancellous bone. On the other hand, the numerical results of L3-L5 demonstrate that the highest tensile and compressive principal strains were generated on the posterior vertebral rims, and on the pedicles and pars interarticularis. Through the comparative study, it was confirmed that the calculation results related to L5 and L3-L5 were in close agreement with the experiments. Based on the introduced method, the vertebral failure as well as the stress-strain behavior can be specifically identified.