$eta$-SiC whiskers could be formed from a system of mullite-carbon-hydrogen by VLS mechanism at elevated temperatures. It was considered that methane gases were generated from the reaction of hydrogen gases with carbon black, and were reacted with mullite to produce two kinds of gases; silicon suboxide (SiO) and carbon monoxide (CO) of precursors of SiC. With increasing the synthesizing temperature up to 146$0^{circ}C$, the formation of $eta$-SiC whisker increased from 0.58 mg/$ extrm{cm}^2$ to 3.98 mg/$ extrm{cm}^2$ on the basis of unit area of carbon block, and the diameters of whiskers had their uniformity due to the reduction in stacking faults.