Objective To evaluate the efficacy of additive manufacturing scoliosis orthosis, by simulation on interaction of the bone, trunk and orthosis using finite element method. Methods Combined with CT data of the patients, three-dimensional (3D) scanning model of the trunk and full length X-ray of the spine, the bone-trunk-orthosis finite element model was established and proved to be effective. The change and development trend of Cobb angle of the main thoracic scoliosis was calculated under different boundary and load conditions. Results The treatment effect of the additive manufacturing scoliosis orthosis was good. With the increase of orthotic preload, the improvement of Cobb angle and pelvic tilt was more obvious. The Cobb angle was expected to decrease by 6.18° after application of 70 N preload to the orthosis for 6 months. In the case of increasing system stiffness, Cobb angle improvement was not obvious and became even worse. Conclusions Additive manufacturing scoliosis orthosis is effective for treating adolescents with immature bones, while for patients with mature or degenerative bones, its treatment effect is poor.