［Objective］To assess the clinical effects and the improvement of the cervical sagittal alignment after cervical decompression and fusion in severe adolescent cervical kyphosis. ［Methods］Between July 2012 and June 2017, 18 patients with severe adolescent cervical kyphosis underwent cervical decompression and fusion were studied retrospectively. Thirteen of them underwent anterior cervical decompression and fusion, while the other five underwent combined anterior and posterior approach cervical decompression and fusion. Parameters including kyphosis levels, regional kyphosis angle, C2-C7 angle, C0-C2 angle, C7 slope and C2-C7 sagittal vertical axis (SVA) were measured on lateral radiographs in the neutral position for each patient. The preoperative and postoperative visual analogue scale (VAS) of neck pain, neck disability index (NDI) and Japanese Orthopaedic Association (JOA) scores were also compared. ［Results］All the patients were followed up for 24 to 36 months, with a mean of 27.33±5.53 months. The average operation time was 211.67±47.68 minutes and the average blood loss was 404.44±181.01 ml. The mean vertebral number in kyphotic region was 3.83±0.62．The average regional kyphosis angle was corrected from preoperative 51.67°±8.57° to postoperative 9.83°±3.09°, with a correction rate of 80.98%, and 12.89°±4.08° at last follow-up, with a correction loss rate of 7.31%. The average C2-C7 angle and C0-C2 angle were improved after surgery and at last follow-up, while the average C7 slope and C2-C7 SVA were not significantly improved The average postoperative VAS, NDI and JOA scores were improved significantly compared with preoperative data． ［Conclusion］ Anterior cervical decompression and fusion, or combined anterior and posterior approach cervical decompression and fusion, is effective and safe for correcting severe adolescent cervical kyphosis. Significant correction and improvement in regional kyphosis angle, C2-C7 angle and C0-C2 angle were observed.