The batch stability of ceramic powders is a core indicator that manufacturers of ceramic products are most concerned about, yet has long been undocumented. In this study, the similarity of Si₃N₄ powders produced in different batches was quantitatively evaluated by taking combustion-synthesized Si₃N₄ powders as the sample. A system of powder performance evaluation parameters covering static physicochemical and dynamic flowability indices was firstly constructed. Then, all performance data of Si₃N₄ powders in this parameter system were retested. Subsequently, the consistency evaluation data of Si₃N₄ powders were obtained using the cosine similarity method and the Euclidean distance method. The results show that both methods based on this parameter system can reflect the similarity between batches of powders and quantitatively show the differences between them. Calculation results of the two methods are mutually verified. For powders judged to be dissimilar, differences in the process were traced to find the key link in the consistency between the Si₃N₄ powders and the raw silicon powders. For powders judged to be highly similar, they were classified as the same class. These study provides a quantitative basis for the classification of different batches of silicon nitride powders. The “Powder Consistency Evaluation System” established in this work presents an effective evaluation tool and quantitative basis for batch stability (performance consistency) of silicon nitride powder.