Abstract: High-quality silicon nitride ceramic powder was prepared by direct nitriding method, using silica powder as raw material, and the effects of nitriding temperature, heating rate, silica fume particle size and diluent dosage on the powder were explored. The raw silicon fume D50 was 275.36 nm, without Si3N4 diluent, when the reaction temperature was 1400 ℃, the heating rate was controlled at 5 ℃/min at 1100~1400 ℃, the silicon fume was completely nitrided, and spherical silicon nitride materials with uniform particle size (particle size range of 396~458 nm) were prepared. The material has good dispersion, and the mass fraction of the α phase is as high as 95.02%. The results showed that the heating rate was the key factor controlling the reaction process. when the heating rate was too fast or too slow, the conversion degree of silicon nitride from α phase to β phase exceeded the internal reaction degree, and the silica fume reaction was incomplete. The addition of Si3N4 diluent reduced the nitriding temperature. The research results provide a technical basis for the optimization of industrial production process of silicon nitride ceramic powder.