SiC is fabricated by chemical vapor deposition (CVD) on graphite and Si3N4 ceramic respectively. The morphology, composition, grain size and electrical conductivity of SiC deposited on graphite (CVD-SiC(C)) and on Si3N4 ceramic (CVD-SiC(N)) are investigated and compared. The morphology of CVD-SiC(C) and CVD-SiC(N) is much different with each other. The grain size of CVD-SiC(C) is bigger than that of CVD-SiC(N). It is nearly stoichiometric in CVD-SiC(C), while carbon-rich in CVD-SiC(N), so the electrical conductivity and dielectric loss of CVD-SiC(N) are much higher than that of CVD-SiC(C). As the annealing temperature increases, the grain size and electrical conductivity of CVD-SiC(C) and CVD-SiC(N) both increase.