The aim of our study was to explore risk factors of cage nonunion after anterior cervical discectomy and fusion (ACDF). 295 patients underwent ACDF in our hospital between Jan. 2014 and Jan. 2017. Of them, 277 patients suffered cage union (union group, UG) after 6-month follow-up and 18 did not (nonunion group, NG). We collected possible factors including gender, history of smoking, alcohol, hypertension, heart disease, diabetes, body mass index, diagnose, and preoperative visual analog scale -neck, visual analog scale-arm, neck disability index (NDI) and Japanese Orthorpaedic Association, surgical duration, blood loss, fusion levels, superior fusion segment, angle of C2-C7, range of motion for C2-C7, C2-C7 sagittal vertical axis and T1 slope. We performed univariable and multivariable analysis to compare data in 2 groups. The rate of cage nonunion after ACDF was 6.1% (18 of 295) in our study. The outcome of univariable analysis showed that age (63.5 +/- 10.1), angle of C2-C7 (18.0 +/- 4.6), range of motion of C2-C7 (32.5 +/- 7.7), C2-C7 sagittal vertical axis (17.9 +/- 4.3) and T1 slope (22.1 +/- 5.3) were higher in NG than these (59.4 +/- 9.2, 16.2 +/- 4.5, 30.2 +/- 6.9,16.1 +/- 4.0, 20.9 +/- 4.9) in UG. Additionally, patients with osteoporosis had markedly higher rate of cage nonunion after ACDF than those without. What's more, the multivariable analysis implied the same results with univariable analysis. Many factors could predict cage nonunion after ACDF. Cervical sagittal parameters play an important role in cage nonunion after ACDF. We hope that we can provide some guidance for spine surgeon before performing ACDF.