[Objective] To analyze the relationship between cervical extensor (NEM) atrophy and changes in cervical sagittal parameters after single posterior cervical opening. To explore the relationship between functional exercises and changes in sagittal parameters after posterior cervical laminoplasty. [Method] A total of 128 patients who underwent posterior cervical single-door laminoplasty in our hospital from January 2015 to July 2019 were selected. Data of these patients were collected before the operation, 1 week after the operation, 1 year after the operation, and 2 years after the operation. At four time nodes, the sagittal parameters of the patient’s cervical spine were measured using x-ray images, including C2-C7 cobb angle, C2-7 sagittal vertical axis (SVA), and the angle between the upper lamina of T1 and the horizontal plane (T1 slope) ). With magnetic resonance images to measure the abundance of NEM and the rate of steatosis in patients. Correlation analysis of NEM muscle abundance and fat content with cervical sagittal parameters at the last follow-up. [Results] The preoperative SEA/VBA, DEA/VBA, and NEM fat content were significantly different from the measured values at 1 week and 1 year after the operation. At the last follow-up, C3/4 muscle DEA/VBA was positively correlated with C2-7SVA changes (R=0.382, P<0.05), while C3/4 muscle fat content was negatively correlated with C2-7SVA changes (R=-0.494, P <0.05). The SEA/VBA of C3/4, C4/5, and C5/6 were all positively correlated with the change of C2-7Coob angle (R=0.452, 0.379, 0.234, P<0.05;). The DEA/VBA of C3/4 and C4/5 were positively correlated with the change of C2-7Coob angle (R=0.417, 0.266, P<0.05). The fat content of C3/4NEM was negatively correlated with the change of C2-7Coob angle (R=-0.352, P<0.05). The NEM fat content of C7/T1 is positively correlated with the change of T1S (R=0.406, P<0.05) [Conclusion] The sagittal parameters of the cervical spine after posterior cervical laminoplasty change, with the cervical spine has a trend of kyphosis. The posterior cervical extensor atrophy has a certain correlation with the changes of the cervical spine sagittal parameters. The patient''s adherence to postoperative neck muscle exercise can effectively restore the long-term neck muscles and improve the changes in the parameters of the cervical spine after the single-opening posterior cervical door.