Large-scale SiC fibers with diameters of 0.2-1 mum and the maximum length of 3mm. were fabricated through combustion synthesis of Si and C powders with addition of carbamide which is also named as urea. The fabricated fibers are single crystals and have hexagonal structure. The weak exothermic reaction of Si + C --> SiC fibers can be ignited by the strong exothermic reaction of Si + N-2 --> SiN3. Vapor-liquid-solid (VLS) and vapor-solid (VS) mechanisms must be involved in the formation of SiC fibers. Addition of carbamide plays a key role in the formation of SiC fibers, which can act as solid nitrogen source, provide a sufficient space, and promote the growth of fibers.