Abstract Objective Through the finite element analysis to explore the stress changes of the intervertebral disc and the posterior longitudinal ligament before and after the open-door laminoplasty for cervical spine, so as to provide help for the correct understanding of the natural development process of the ossification of the posterior longitudinal ligament(OPLL). Methods According to Mori''s morphological classification of OPLL, 3 cases of C4 / 5 OPLL were selected respectively. The CT images of the patients before and after the operation were introduced into Mimcs 14.0 to structure recognition, and then in Geomagic studio10.0 and HyperMesh 11.0, three-dimensional reconstruction and gridding were carried out for each anatomical structure. According to the actual situation of the human body, the gravity load of the head was loaded, and the flexion, extension and rotation loads were added to the head centroid to simulate the movement of the head. and the von Mises stress was observed in ABAQUS 6.12. Results ① the stress of C4 / 5 and C5 / 6 discs in the control group was significantly lower than that in the observation group (P < 0.05). The C4 / 5 and C5 / 6 disc stress of isolated and continuous models were significantly lower than that of segmental model under flexion and rotation loads (P < 0.05). ② The stress nephogram of the posterior longitudinal ligament showed that the stress of C4 / 5 segment in the observation group was the largest, and gradually weakened along the shape of the posterior longitudinal ligament to both sides of the head and tail, while the stress distribution of the posterior longitudinal ligament in the control group was more uniform. ③The stress of the posterior longitudinal ligament in the observation group was significantly higher than that in the control group (P < 0.01). and isolated and continuous models were significantly higher than that of segmental model under flexion and rotation load (P < 0.01). ④ There was no significant difference in the stress changes of C4 / 5 and C5 / 6 discs and posterior longitudinal ligament between the two groups (P > 0.05) before and after the open-door laminoplasty for cervical spine.Conclusions The open-door laminoplasty for cervical spine could restore the integrity of the posterior structure, but it colud not change the stress state of the posterior longitudinal ligament. The ossification of isolated and continuous posterior longitudinal ligament would significantly increase the stress of the posterior longitudinal ligament.