Under the condition of long-term weightlessness,astronauts suffer from weightlessness osteoporosis.In order to explore the effect of bone loss on the lumbar bearing capacity,the lumbar spine mechanics experiment with different bone densities was designed.The three-dimensional model of lumbar vertebrae was established by image processing,and the lumbar vertebrae stress was obtained by finite element algorithm(FEA).By comparing the stress results of lumbar models with different material properties,the results showed that the stress value of lumbar spine in osteoporosis was smaller than that of normal lumbar vertebrae,but the deformation was significantly increased. It can be seen that bone loss will lead to changes in the performance of lumbar bones, increasedlumbar deformation,and decreasedlumbar structural load capacity.