The invention provides a novel method for the preparation of silicon carbide fibers capable of being performed at a relatively low temperature and giving fibers of relatively large lengths by the vapor-phase pyrolysis of an organosilicon compound on a substrate. The method comprises contacting an organosilicon compound, which should have no halogen and oxygen atoms directly bonded to the silicon atoms and have preferably at least one hydrogen atom directly bonded to the silicon atom in a molecule, with a finely divided powder of a metal or a compound of a metal, such as copper, silver, vanadium, niobium, tantalum, iron, cobalt, nickel, palladium and platinum, at a temperature of 700.degree. to 1450.degree. C. so that the powder serves simultaneously as a catalyst and nucleus for the growth of the silicon carbide fibers thereon formed by the pyrolysis of the organosilicon compound. When the organosilicon compound is deficient of the carbon content relative to the silicon so that free silicon may be formed by the pyrolysis, admixing of a hydrocarbon to the feed of the organosilicon compound can solve the problem.