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 the 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 the performance data of Si3N4 powders in this parameter system were tested and obtained. Subsequently, the consistency evaluation data of Si3N4 powders were obtained using the cosine similarity method and the Euclidean distance method, respectively. The results show that both the cosine similarity and Euclidean distance based on this parameter system can reflect the similarity between batches of powders and quantitatively show the differences between them. The 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 control of Si3N4 powders-the raw silicon powder. For powders judged to be highly similar, they were classified as the same class. It provided a quantitative basis for the classification of different batches of silicon nitride powders. The "Powder Consistency Evaluation System" established in this work provides an effective evaluation tool and quantitative basis for batch stability (performance consistency) of silicon nitride powder product quality.