Adolescents’ poor sitting posture is hazardous, and long-term poor sitting posture can lead to elevated incidence of neck pain. This study investigated the biomechanical attributes of the adolescent neck to mitigate the hazards of poor sitting posture and to provide recommendations for adolescent neck health; The C1-T3 images of the cervical region were acquired from the same subject in normal posture as well as in cervical forward flexion posture with a gap between scans of 0.50mm, and the CT images were transformed into DOCM format in Mimics for subsequent 3D modelling. A finite element (FE) model of the C1-T3 normal posture as well as the cervical forward flexion posture was established. In order to investigate the differences between the two models’ cervical vertebrae and intervertebral disc stress, the stress and intervertebral disc strain of the two models were compared. A standard cervical spine model and a FE model for cervical forward flexion were created and validated. The range of motion, vertebral body, and intervertebral disc stresses were examined for both models. Comparison with previous literature confirmed the accuracy of the forward flexion model, showing consistent results with the normal cervical spine model. In the forward flexion direction, the model demonstrated increased stresses in the vertebral body, particularly in the anterior side, surpassing those in the normal model. The maximum stress in the vertebral body reached 5.99 MPa, and in the intervertebral disc, it was 1.02 MPa. Overall, stresses in the anterior cervical flexion model exceeded those in the normal model. Poor neck posture leads to more pronounced stress concentration phenomena in the vertebral body, increasing peak pressure in the vertebral body, in addition increasing com-pression on the intervertebral discs, leading to an increased risk of neck pain risk as well as cervical dysplasia, and therefore excessive forward flexion of the cervical spine in adolescents should be avoided.