Abstract: This study proposes a flexible multibody dynamics modeling approach for the thoracolumbar spine of scoliosis patients based on medical imaging and geometrically exact beam formulation (GEBF). It aims to investigate the influence mechanism of spinal scoliosis on human vibration responses through vibration modal and transmissibility analyses. Three-dimensional geometric parameters of the scoliotic spine were extracted from anteroposterior and lateral radiographs and integrated with kinematic rhythm constraints to adjust a spinal musculoskeletal dynamics model to fit the scoliotic configuration. On this basis, the intervertebral discs (IVDs) and their adjacent vertebrae were simplified as geometrically exact beam elements, where the rotational vector at each node corresponded to the three-dimensional vertebral posture. The element stiffness matrix was linearized from intervertebral stiffness incorporating contributions of IVDs, ligaments, and muscles. Furthermore, modal and vibration transmissibility analyses of the scoliotic spine were conducted to explore the influence mechanisms of scoliotic spine morphology on the biodynamic response. Numerical results of natural frequencies and sit-to-head transmissibility ratios aligned with experimental measurements in the literature. Additionally, the scoliotic spines exhibited coupled vibration characteristics in the sagittal and coronal planes, and the vibration out of the sagittal plane reduced the sit-to-head vibration amplitude. The proposed methodology provides a flexible multibody dynamics modeling and analysis framework for revealing subject-specific human-related vibration mechanisms in scoliotic patients, offering theoretical support and quantitative analysis models for vehicle vibration comfort evaluation and clinical rehabilitation strategy development.