Objective To establish a numerical calculation and analysis model of lumbar disc herniation so as to provide a method of detecting and assessing the mechanical mechanism of lumbar disc herniation. Methods Based on CT of a healthy adult, the vertebra and intervertebral disc of lumbar 4~5 segment were reconstructed by Mimics 10.01 software and Geomagic 10.0 software, respectively. By adding the lumbar attaching ligaments and transforming the corresponding material properties of the extruded disc in Ansys software, the finite element model of L4~5 was established to create the intact disc and extruded disc model. The finite element method was employed to simulate the biomechanical properties of the two models under the loads of axial compression, flexion, lateral bending, extension and rotation. Results After the lumbar disc was extruded, the stress distribution on the disc and the ability of load transfer were changed. The stress was concentrated at the posterior lateral of annulus fibrous. Under the same loads, the maximum deformation of the extruded disc was larger than that of the intact disc. The contact forces of the facet joints in the extruded disc model were larger than that in the intact disc model. Conclusions After the lumbar disc was extruded, the load-bearing capacity was decreased and the stress level of the articular process was increased, and the loads on the facet joints were also enhanced, leading to the decline of stability in the lumbar vertebrae.