Well-separated alpha -Si3N4 and beta -SiC nanorods have simultaneously been synthesized by the reaction of SiO2 nanoparticles and active carbon at 1450 degreesC in nitrogen atmosphere. TEM (transmission electron microscopy) photographs confirm alpha -Si3N4 nanorods with the diameter of 10-100) nm and length up to 15 mum. and beta -SiC nanorods with the diameter around 40 nm and length up to about 1 mum. The chemical reaction conditions and mechanisms have been discussed.