Based on DICOM images of the human body, an L4/5 segment three-dimensional finite element model that more closely conforms to the anatomical structure of the human body was established to simulate the biomechanical responses of the lumbar spine under four motion states: flexion, extension, lateral bending, and torsion. After ALL injury, the ROM of the lumbar spine increases, with the most significant increase during extension. After ALL damage, the stress decreases and the distribution changes. During extension, the maximum stress position shifts from the upper part of the ligament to the lower part of the ligament, and the stress action range significantly decreases during lateral bending. After ALL damage, the strain distribution changes to varying degrees, resulting in significant longitudinal deformation. In other motion states except torsion, the ALL strain increases, with the largest increase in extension and lateral bending strains. ALL mainly restricts backward extension movement, and lumbar stability decreases after ALL injury. Patients with impaired ALL should minimize excessive extension and lateral bending movements, which may aggravate existing injuries during extension and lateral bending movements. This simulation experiment provides support and reference for the diagnosis and treatment of ligament injury diseases.