Objective To make comparative analysis on mechancial properties of the modified cortical bone trajectory (MCBT) nailing technique using a novel variable-diameter screw and the traditional pedicle nailing technique using the cement-augmented pedicle screw (CAPS) in the L4 vertebral body. Merthods CAPS and MCBT instrumentation in the L4 vertebral body model were established by obtaining CT scan data from osteoporotic patients. The finite element method was used to compare the stability, screw axial pull-out force and lumbar spine motion under four working conditions (upper, lower, left and right loads) by using different nailing techniques. Results The axial pull-out force of the screws in MCBT group was 25.3% higher than that of the CAPS group (P<0.05); the load-displacement ratios of the screws in MCBT group were 14.9% (P>0.05), 23.2% (P>0.05), and 19.1% (P<0.05) higher than those of CAPS group under the lower, left, and right working conditions, respectively; the load-displacement ratios of the screws in MCBT group were slightly lower than those of CAPS group under the upper working condition, but the differences were not statistically significant (P>0.05); under the anterior and posterior flexion conditions, the lumbar spine motion of MCBT group was reduced by 13.3% and 2.5%, respectively, compared with CAPS group; under the left lateral bending, right lateral bending, and axial rotational conditions, the lumbar spine motion of MCBT group was improved by 69.1%, 74.6%, and 118.1%, respectively, compared with CAPS group, but these difference were not statistically significant (P>0.05). Conclusion MCBT screw was slightly better than CAPS in axial resistance to extraction force, and stability of vertebral anterior flexion under lower, left and right working conditions, and slightly weaker than CAPS in stability under upper, left lateral bending, right lateral bending, and axial rotational working conditions. This study demonstrates that MCBT screw has certain advantages over CAPS, and it provides a pre-basic foundation for the clinical application of MCBT nailing technique for treating osteoporosis.