A nonrandomized and prospective study. To compare clinical outcomes and sagittal alignment after 1-level, 2-level, and 3-level anterior cervical discectomy and fusion (ACDF) in patients with cervical spondylotic myelopathy (CSM). ACDF is a widely used surgical approach for CSM. It remains controversial regarding to whether corrected lordosis can be maintained over time after different levels ACDF. 175 patients with CSM who underwent ACDF were enrolled in this retrospective study. The neurofunctional assessment was performed with the JOA score and the recovery rate of JOA score. Radiographic parameters included C2-C7 lordosis (CL), fused segments lordosis (FL), T1 slope, the cervical sagittal vertical axis (cSVA). Patients with more fusion levels had more operative time and blood loss and higher rate of complications. All patients showed a larger cervical lordosis than that preoperatively and the restored lordosis increased with more segments involved. the restored lordosis had little change during the whole follow-up in 1-level and 2-level group. CL decreased from 25.65 ± 9.31° on the third postoperative day to 20.25 ± 10.03° at the final follow-up in 3-level group (p = 0.001). Only T1 slope in 3-level increased significantly from preoperative 26.55 ± 9.36° to 29.06 ± 7.54° on the third postoperative day (p = 0.011) and decreased to 26.89 ± 7.22 ° (p = 0.043) at final follow-up. The JOA score all increased significantly at the last follow-up in each group, but the recovery rate of the JOA score in each group was similar (p = 0.096). ACDF with different levels had similar postoperative clinical outcomes. 3-level ACDF has an apparent advantage in restoring lordosis, a poor ability to maintain lordosis and a higher incidence of complications compared to 1-level or 2-level ACDF. 4.