Objective To investigate correlation between preoperative C2 slope (C2S) and effectiveness at 2 years after short-segment anterior cervical discectomy and fusion (ACDF), with the aim of providing reliable indicators for predicting effectiveness. Methods Patients with cervical spondylotic myelopathy who received short-segment ACDF between January 2018 and December 2022 were enrolled as the study subjects. Among them, 118 patients met the selection criteria and were enrolled in the study. There were 46 males and 72 females, aged from 26 to 80 years, with a mean age of 53.6 years. The operative duration was (127.6±33.46) minutes and the intraoperative blood loss was (34.75±30.40) mL. All patients were followed up for 2 years. The pre- and post-operative Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) score, and visual analogue scale (VAS) score for pain were recorded. Based on the anteroposterior and lateral cervical X-ray films, the sagittal parameters of the cervical spine were measured [C2-C7 Cobb angle, C0-C2 Cobb angle, T1 slope, C2S, sagittal segmental angle (SSA) of the surgical segment, and average surgical disc height (ASDH) of the surgical segment]. Statistical analyses were performed to assess the differences in these indicators between pre- and post-operation, as well as the correlations between the preoperative C2S and the JOA score, NDI, and VAS score at 2 years after operation. The patients were allocated into group A (C2S >11.73°) and group B (C2S≤ 11.73°) according to the median value of the preoperative C2S (11.73°). The JOA score, NDI, and VAS score before operation and at 2 years after operation, as well as the differences between pre- and post-operative values (change values), were compared between the two groups. Results The T1 slope, C2-C7 Cobb angle, C0-C2 Cobb angle, SSA, and ASDH at immediate after operation and JOA score, NDI, and VAS score at 2 years after operation significantly improved in 118 patients when compared with preoperatively (P<0.05). Pearson correlation analysis showed that preoperative C2S was not correlated with JOA score and NDI at 2 years after operation (P>0.05), but negatively correlated with VAS score (P<0.05). There were 59 patients with preoperative C2S>11.73° (group A) and 59 with C2S≤11.73° (group B). There was no significant difference in preoperative JOA score, NDI, and VAS score between the two groups (P>0.05). There were significant differences in VAS score at 2 year after operation and the change value between the two groups (P<0.05); there was no significant difference in the JOA score and NDI (P>0.05). Conclusion Patients with cervical spondylotic myelopathy and a higher preoperative C2S exhibited superior long-term pain relief and effectiveness following short-segment ACDF.