Objective To explore the biomechanical safety of applying traditional Chinese orthopedic manipulation therapy after anterior cervical discectomy and fusion (ACDF) surgery, so as to provide a theoretical basis for clinical treatment in biomechanics. Methods Based on CT data, a three-dimensional finite element model of the normal C0–T1 cervical spine was established, and an ACDF postoperative finite element model of the C5–6 segment was constructed on this basis. Cervical spine rotation manipulation was simulated at the C4 and C7 segments of both models, and the von Mises stresses of the vertebral body, bilateral facet joints, intervertebral discs, and internal fixation system under manipulation loading of the C4 and C7 segments in both models were compared and analyzed. Results The study found that when the C4 segment was manipulated, the stress on the C5, C6, and C7 vertebral bodies in the ACDF postoperative model decreased by 12.3%, 11.5%, and 26.4% ,compared to the normal model. The stress on the left facet joints of the C4–5, C5–6, and C6–7 segments decreased by 12.3%, 58.8%, and 15.4%, and the stress on the right facet joints decreased by 16.6%, 92.1%, and 17.2%. The stress on the C4–5 and C6–7 segments decreased by 13.2% and 4.0% , while the maximum stress of the fusion cage, titanium plate, and screws in the C5–6 segment were 9.349, 111.9, and 300.8 MPa. When the C7 segment was manipulated, the stress on the C4, C5, and C6 vertebral bodies in the ACDF postoperative model increased significantly compared to the normal model, especially the C5 vertebral body, with an increase of nearly 18 times. Except for the stress on the left facet joint of the C4–5 segment increased by 57.7%, the stress on the bilateral facet joints of other segments generally decreased, but the stress on the C4–5 and C6–7 segments increased by 43.2% and 21.7% and the stresses on the fusion cage, titanium plate, and screws in the C5–6 segment were 2.926, 205.4, and 256.2 MPa. Conclusions The safety of performing manipulation on the upper vertebral body of the fusion segment after ACDF surgery is relatively high, but performing manipulation on the lower vertebral body of the fusion segment may lead to stress concentration and increase the risk of injury. When postoperative conservative treatment is implemented, the manipulation safety and indications should be considered to avoid operations in high-risk areas, and more precise and safe manipulation intervention treatment should be implemented based on the specific postoperative biomechanical state of the patient.