Objective To investigate clinical efficacy after posterior open-door laminoplasty with mini-plate and anchor, and the open-door effect measured on CT. Methods From February 2015 to February 2018, 78 patients with multilevel cervical spondylotic myelopathy were retrospectively studied in our department. According to the different fixation methods, all patients were divided into cervical posterior open-door Centerpiece fixation group(group A, 36 cases)and cervical posterior open-door anchor fixation group(group B, 42 cases)．The important clinical data are recorded, including operation time, intraoperative bleeding volume, VAS score of cervical pain, JOA score, improvement rate of spinal nerve function and NDI of cervical spine at pre- and post-operation of 12 months. Some radiological parameters on CT were compared at pre-operation, 3 days and 12 months after surgery, which were the anteroposterior diameter of C3-7, the enlargement rate of cervical canal, the opening angle and the "re-closing" rate. Results There were no significant difference in operation time and bleeding volume between the two groups(P＞0.05). The VAS score, JOA score and NDI score were no statistical difference between the two groups before operation(P＞0.05). At 12 months after surgery, the VAS score and NDI score in the two groups were significantly lower than those before operation(P＜0.05), but the JOA score was higher(P＜0.05).There was no statistical difference in VAS score, JOA score and improvement rate of spinal cord nerve function between the two groups (P＞0.05), while the NDI score in group A was better than that in group B(P＜0.05). In radiological parameters, the anteroposterior diameter of C3-7 between the two groups was similar before surgery(P＞0.05), but the diameter both increased after operation(P＜0.05). At 3 days after operation, the anteroposterior diameter of C3-7 in group A was smaller than that in group B(P＜0.05), and there was no significant difference in the opening angle in both gourps(P＞0.05). At 12 months after surgery, the anteroposterior diameter of C3-7 had no difference between the two groups(P＞0.05). The opening angle in group A was larger than that in group B(P＜0.05). The "re-closing" rate had statistical difference in both groups(P＜0.05). Conclusion Posterior open-door laminoplasty with mini-plate and anchor can achieve good clinical results in the treatment of multi-level cervical spondylotic myelopathy, but the cervical function after mini-plate is better than that of anchor. The open-door effect of the anchor would be partially lost.