Objective to compare the biomechanical properties of traditional trajectories (TT) screws and cortical bone trajectories (CBT) screws fixation in lumbar vertebrae by finite element method. The samples were extracted from the computed tomography (CT) data of patients with osteoporosis to establish the finite element model of L1-L5 whole vertebral functional unit osteoporosis. After simulating the two fixation methods of TT screw and CBT screw, the model measured and compared the stress distribution, the maximum stress value and the difference between the two methods. The results show that under the same fixation mode, the stress distribution of CBT group is significantly different in the same load state. Different screw path leads to different bone mineral density, which directly affects the mechanical properties of internal fixation screw in lumbar spine. Different implant angle also affects the stress distribution and the maximum stress value. The mechanical properties and performance of L1-L5 vertebral bodies are different with different shapes and sizes. So, CBT screw technique is an optimal method for lumbar internal fixation in patients with osteoporosis. However, for the five segments of lumbar, we need to take different treatment for different vertebrae.