In combination with a planetary ball-milling machine, a Ni–Al₂O₃ catalyst was prepared by a mechanochemical method. The effect of Ni loading on the crystal structure, reduction characteristics, and hydrogenation performance of the Ni–Al₂O₃ catalyst was investigated. The prepared catalysts were characterized using EDX, XRD, H₂-TPR, BET, TEM and NH₃-TPD methods. The results of the XRD characterization showed that the peak intensity of the active Ni component increased with an increase in the Ni content. The ratio of the measured Ni content to the theoretical Ni content of the MC25% and MC30% samples exceeded 1.1. As the Ni addition was increased up to 10%, the sample consisted of uniform spherical particles, which could provide more contact surfaces. The medium acid peak temperature shifts towards the high temperature direction as the Ni loading increased from 5% to 20%, and then (>20%) decreased to a lower temperature. The corresponding peak area firstly increased and then decreased, presenting a visual representation of changes in the number of acid centers on the catalyst. Evaluation of the results showed that the MC20% catalyst presented a large specific surface area of 279 m² g⁻¹, and it showed good hydrogenation performance, with a BYD conversion of 25.0%, BED selectivity of 89.3%, and BED yield of 22.3%.