Mixtures of carbon and silica (about 0.46${mu}{ extrm}{m}$) which was synthesized by the hydrolysis of ethyl silicate, the molar ratio of silica/carbon was fixed as 1/10(weight ratio : 1/2), were nitrided in the temperature range 135$0^{circ}C$~150$0^{circ}C$. The phse of the product Si3N4 was $alpha$ phase and the morphology was hexagnoal prism and the nitridation reaction was completed in 5 hrs at 150$0^{circ}C$ or 7hrs at 145$0^{circ}C$. The reaction rate above 150$0^{circ}C$ was diffusion-controlled, following Jander equation. Activation energy Q was derived from the Arrhenius plot and the value was about 101kcal/mol. Axis ratio of Lattice constants(c/a) was 0.726 and unit volume was $AA$3, the larger the molar ratio of carbon/Alkoxide was, the smaller the particle size of $alpha$Si3N4 was.