Abstract Objective: To establish a finite element model (FEM) for upper cervical vertebrae at C0-3 with Jefferson fracture, and to analyze the influence of atl0061ntoaxial fusion (posterior atlantoaxial fusion, PSF) and occipitocervical fusion (OCF1, OCF2) on the mechanical properties of vertebral body biomechanics and mechanical conduction of screw-rod system. Methods A model of upper cervical vertebrae C0-3 segment Jefferson fracture was established based on CT images. The stress distribution and joint activity of cervical vertebrae, the maximum stress of screw-rod system and the stress distribution of intervertebral disc were studied by using PSF, OCF1 and OCF2 internal fixation based on clinical operation. Results: The total ROM of the upper cervical spine was 2.0°, 2.0°, 1.0°, 2.1°,2.5°, 1.5°, 1.5°, 1.9° and 2.0°, 1.5°, 1.8°, 1.7°, and the equivalent force values were 56.8, 41.9, 35.2, 57.9MPa, 29.8, 17.7, 25.7, 51.4MPa and 31.2, 17.5, 23.3, 44.7MPa, respectively. The maximum equivalent stress of PSF, OCF1 and OCF2 were 213.9, 168.1, 150.0MPa, 14.9, 9.8, 8.5MPa respectively. The stress was concentrated on the upper and lower cartilage endplate and screw root respectively. Combined with clinical results, OCF2 showed a better fixation effect. Conclusion: PSF, OCF1 and OCF2 can reduce the ROM of the upper cervical vertebrae and reconstruct the stability of the upper cervical vertebrae.