The particle size of synthesized SiC powders was decreased with increasing carbon content when the mixture of carbon and silica was carbonized at 1, 45$0^{circ}C$ after hydrolysis of the mixture with the ranges of 3.1 to 3.5 in the mole ratio of Carbon/Alkoxide. The reacted fraction of $eta$-SiC nearly had nothing to do with the mole ratio of Carbon/Alkoxide. When the reaction was made by adding 0.5wt% additives in the composition of 3.1 in the mole ratio of carbon/alkoxide, the additives decreased the yield of $eta$-SiC and its sequence was Ba2O3>B>Fe>Al>Al2O3>Si. The effect of additives promoted the transformation of $eta$-SiC to $alpha$-SiC form and shwoed the increasing tendency of lattice constant. The two colors of $eta$-SiC powder came out : one was the black grey with addition of Al, Al2O3 and B the other the light grey with addition of Fe, B2O3 and Si.