3C-SiC nanowires were synthesized in Ar atomosphere via Co nanoparticle catalytic reaction with expanded graphite and silicon powders as raw materials and Co(NO3)2·6H2O as a catalyst precursor. The effects of reaction temperature and catalyst addition on the formation of SiC nanowires were investigated. The phase composition and microstructure of the as-prepared products were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The optoelectronic property of as-prepared 3C-SiC nanowires was analyzed. The results show that Co catalyst promotes the growth of 3C-SiC nanowires and decreases the complete reaction temperature and the formation temperature. 3C-SiC nanowires could be synthesized at 1 573 K for 3 h using 3.0% Co as catalysts at C/Si molar ratio of 1:1. The formed 3C-SiC nanowires are approximately 50-60 nm in diameter and tens micrometers in length. According to the results by the first-principles calculation, the activities of the reactants are increased via dwindling the bonding strength of C=C, Si-O and C-O bonds. The room-temperature PL spectra indicate that the as-synthesized 3C-SiC nanowires have a special emission at 307 nm (4.04 eV), which could be used as a potential material for optoelectronic nanodevices.