Abstract Objective To retrospectively analyze the effect of C3 laminectomy and laminoplasty on the sagittal parameters and prognosis of cervical spine after posterior cervical open-door laminoplasty.Methods From January 2018 to December 2019, 56 patients with cervical spondylotic myelopathy were divided into observation group and control group according to the different treatment methods of C3 lamina. The observation group (31 cases) received C3 laminectomy, and the control group (25 cases) received C3 laminoplasty. The perioperative data, JOA score, Visual analogue scale(VAS) and cervical sagittal parameters including C2-7 Cobb angle and C2-7 SVA were observed.Results ①The operation time of the observation group was less than that of the control group, and the difference was statistically significant (P > 0.05).② All patients were followed up for 8 to 12 months, with an average of 9.73 months. At the last follow-up, JOA scores were significantly higher than those at 1 month after operation (P < 0.001). But the VAS score of the observation group was significantly lower than that of the control group (P < 0.001). There was no significant difference in preoperative c2-7 Cobb and c2-7 SVA between the two groups (P > 0.05). ③There was no significant change in C2-7 Cobb before operation. At the last follow-up, C2-7 SVA in the control group was significantly higher than that before operation (P < 0.001), while there was no significant difference in C2-7 SVA between the observation group and that before operation (P > 0.05).Conclusions C3 laminectomy could increase the anterior stability of cervical spine and reduce the influence of traditional laminoplasty on the sagittal stability of cervical spine.