Objective To analyze factors that affect axial mechanical performance of the posterior pedicle fixation system. Methods The mechanical model for axial mechanical properties of the posterior pedicle fixation system was established to perform mechanical analysis. By referring to the Standard YY/T 0961-2014, tests on axial ejection force and axial clamping torque of JHL-I multi-axis components, JHL-I single-axis components, JHL-V multi-axis components and JHL-V single-axis components were performed by using Instron E3000 and Instron E10000 mechanical testing machines. Results The ejection rigidity of the single-axis component of vertebral nail system was significantly higher than that of the multi-axis component of vertebral nail system; the torsion rigidity of JHL-V was higher than that of JHL-I. The type and size of the locking bolt as well as its locking torque were the main factors affecting axial ejection force of the posterior spinal pedicle fixation system; the size of the locking bolt and the diameter of the connection rod were the main factors affecting axial clamping torque of the system; axial mechanical properties of the system could be improved by increasing the diameter of the connecting rod, the coefficient of friction between each connecting element, and the pitch diameter of the locking bolt. Conclusions The research findings provide references for optimizing and improving axial mechanical properties of the posterior pedicle fixation system.