The present study describes a novel method to improve the dispersibility of silicon nitride powders in aqueous media. Specifically, a new Si3N4@g-C3N4 core–shell composite material was synthesized via annealing the mixture of silicon nitride and melamine under a nitrogen atmosphere using heating method. The effects of various initial mass ratios of Si3N4 and melamine on the structure and dispersibility of the composite were systematically investigated. The results of X-ray photoelectron spectroscopy and transmission electron microscope demonstrated that as-obtained Si3N4@g-C3N4 composite powders possess the core–shell structure, whereas the zeta potential and sedimentation analysis showed that they exhibit good dispersion in aqueous media. Furthermore, the colloidal dispersion of the composite powders is most stable when the initial mass ratio of Si3N4 and melamine is 100:3. The coated g-C3N4 could be completely removed in a cryogenic nitrogen atmosphere. The proposed process is expected to provide novel avenues for the study of dispersion of other inorganic powders. Si3N4@g-C3N4 composite powders were obtained through chemical dipping method. The results showed that the dispersibility of the composite powders was far better than that of native Si3N4 powers. Among the as-prepared Si3N4@g-C3N4 composite powders, Si3N4@3%g-C3N4 samples presented the optimum dispersibility. Notably, g-C3N4 coating could be removed completely by heating sublimation, which signifies that this modification would not bring any impurities. [ABSTRACT FROM AUTHOR]