Low back pain is a common orthopedic disease. Degeneration of lower lumbar is the main reason for adult low back pain. Research shows that approximately 5% of adults have degenerative low back pain. It seriously infects the daily lives of patients. Degeneration of lower lumbar can be divided into degenerative lumbar disc degeneration, endplate degeneration, degenerative annulus fibrosus, spinal degeneration, ligament and muscle degeneration. Among these diseases, disc degeneration,endplate degeneration, degeneration of the annulus fibrosus affect the biomechanics of lumbar spine most seriously. In recent years, with the rapid growth of economic and the continuous improvement of people\'s living standards, health problems have been increasingly emphasized. Treatment of degenerative diseases has also made significant progress. Lumbar spinal fusion is the most important methods to the treatment of degenerative diseases. However, with the increasing success of fusion, the effect of the treatment has not been obvious. As a result of this fusion, the rigid fixation causes stress shielding which leads to the degenerative disease of adjacent segment. The majority of patients with low back pain follow the multiple segment degeneration. After the fusion, the adjacent segment with slightly degeneration accelerates its degeneration, which causes low back pain again, and the patients need the surgery again. That will bring financial burden to the patients, and at the same time it will take patients go through a great deal of spiritual suffering. In this paper, we will use the finite element analysis to study the 2, 3, 4 lumbar segments which are reconstructed by the method of CT-based three-dimensional reconstruction. The comparison of the analysis result with the experimental result shows that the three-dimensional finite element model of lumbar vertebrae is reliable. Finally posterior pedicle screw implantation surgery is simulated to analyze the effect of the implanting of pedicle screw to the lumbar.Methods: In this study the three-dimensional model of the lumbar spine is reconstructed based on CT data. Then surgical process of the pedicle screw implantation is simulated. In this process, the reconstruction of the disc has always been the most difficult problem. In this paper Solidworks and Mimics are both used to complete the reconstruction process to solve this problem. During the process of the assignment of the material properties, FEA module of mimics is used to realize the non-uniform material properties assignment of lumbar spine. This method makes the model more similar to the actual lumbar biomechanical properties. It is a good improvement of the lumbar finite element remodeling. The model will be imported into the finite element analysis software ABAQUS and the finite element analysis will be carried out. Compare the analysis results with the vitro experimental results. At last the finite element analysis of the model with the screw is carried out.Results: Comparing the analysis results of the model without screw with vitro experimental results shows that the load and displacement curve of this model is very similar to the curves of other researchers. So the model is reliable and it can be used for further research of lumbar spine diseases. The results of the model have implanted screw show that distribution of stress of the lumbar spine changes greatly, in particularly the intervertebral disc changes the most.Conclusion and discussion: On one hand, we use Solidworks to recinstruct the intervertebral disc. This method can not only describe intervertebral disc more accurately, but also make the adjacent vertebral body and intervertebral disc touch each other closely. It is a good foundation for the finite element analysis. On the other hand, we assigned 150 different material properties to each lumbar section. This method makes the material properties of the model more similar to the real lumbar spine, which significantly improves the reliability of the biomechanical properties of the model. The result from the model without pedicle screw is close to the results of other researchers. In addition, the distribution of the stress of the model is similar to the actual biomechanics of the lumbar spine, e.g. the outer layer of cortical bone is carries on greater load and stress, and the force on the cancellous bone is smaller. The stress concentration occurs on the pedicle screw. All these show the reliability of the model. As the distribution of the stress of the entire model is concerned, the displacement of the model that implanted the pedicle screw is much smaller than the model without pedicle screw under the same static force. This shows that pedicle screw carries on most of the load, and the activity of the lumbar spine is restricted, so that the injured lumbar spine can be protected. But the distribution of the stress of the model which implanted the pedicle screw is much different from the model without pedicle screw, which changes the mechanical environment of the lumbar and it will inevitably result in the vascular changes in the spine. Spinal biomechanics of the movement changes would also lead to the increase of compensatory of adjacent segment. At last it will lead to the occurrence of adjacent segment degeneration. This explains why the spinal fusion can result the adjacent segment degeneration. The stress distribution of the intervertebral disc is changed more obviously. Intervertebral disc absorbs nutrition, ejects metabolic products, plays a physiological function and repairs damage, all these depend on the flowing of the liquid both inside and outside the intervertebral disc. Liquid flowing and different pressure inside and outside the intervertebral disc is the main power of the intervertebral disc. But rigid fixation of the disc changes the mechanics environment that the intervertebral disc absorbs nutrition, and infects the metabolism of intervertebral disc, which will ultimately lead to intervertebral disc lesions.As mentioned above, the model in this study can reflect the biomechanical properties of the lumbar spine, and it can explain the lower lumbar spine degeneration pathogenesis from the perspective of mechanics, it is a good foundation for further study of lumbar fusion, degenerative diseases.