［Objective］To investigate the correlation between adjacent segment degeneration and cervical sagittal parameters after anterior cervical discectomy and fusion.［Methods］Retrospective analysis of 76 patients with cervical spondylotic myelopathy who underwent cervical anterior segmental single-segment discectomy and fusion (ACDF) surgery from January 2012 to December 2017 with complete follow-up data. Data were divided into degenerative and non-degenerate groups based on whether adjacent segment degeneration occurred during follow-up. The general data (sex, age, body mass index, etc.) and cervical sagittal parameters (C2-7 Cobb angle, surgical segment Cobb angle, C2-7 sagittal vertical axis, thoracic inlet angle, T1 slope, neck tilt).The correlation between adjacent segment degeneration and sagittal parameters of the cervical spine was analyzed.［Results］During the follow-up period, 31 cases of adjacent segment degeneration occurred, and 45 cases had no degeneration. There was no significant difference in the baseline sex and age between the two groups (P＞0.05).The parameters of C2-7Cobb angle, surgical segment Cobb angle, C2-7SVA, TIA, T1S, NT, T1S＜19.5° between the two groups were not statistically significant (P＞0.05).The C2-7Cobb angle, surgical segment Cobb angle and T1S in the postoperative degenerative group were lower than those in the non-degeneration group, and the differences were statistically significant (P＜0.05).There were no significant differences in C2-7SVA, TIA and NT between the two groups (P＞0.05).In addition, the proportion of patients with T1S＜19.5°in the postoperative degeneration group was significantly higher than that in the non-degeneration group, and the difference was statistically significant (P＜0.05).［Conclusions］The adjacent segment degeneration after anterior cervical discectomy and fusion is closely related to the sagittal parameters of cervical vertebra. Poor recovery of Cobb Angle at the surgical segment resulted in the loss of C2-7cobb Angle, which further led to cervical sagittal imbalance, which was one of the causes of ASD after ACDF.