Single crystal 6H-SiC nanoribbons were in situ synthesized in large scale on the as-prepared SiC-Si ceramic substrates via a facile heat-treatment approach using ferrocene as catalyst. The as-synthesized nanoribbons were up to several millimeters long, with widths of 200-300nm and thicknesses of 20-80nm. A novel combination growth mechanism of vapor-liquid-solid-based and vapor-solid-tip was proposed for the growth mode of the as-synthesized nanoribbons. This study provided not only a new method for synthesizing SiC nanoribbons but also a new insight into the growth mode for SiC nanoribbons.