A highly pure mixture of carbon and silica was obtained on pyrolysis rice husk leached with acid at high temperature in a nonoxidizing atmosphere. The product was suitable for use as a starting material in the the manufacture of silicon nitride powder. The effect of treatment including the kind and concentration of acid and the pyrolysis temperature on the constituents of the specimen was presented. Kinetic tests on pyrolysis of rice husk in a nitrogen atmosphere were carried out with a thermal gravimetric analysis (TGA) technique at heating rates 2, 3, and 5 k/min. The results indicated that thermal degradation of rice husk consisted of two distinct pyrolysis stages. The corresponding kinetic parameters including the activation energy were determined. A reasonable pyrolysis mechanism was proposed, which agreed satisfactorily with the experimental results.