Multi-walled carbon nanotubes (MWNTs) were coated with nanometer sized SiC layer by magnetron sputtering, and their corrosion resistances in oxygen and gaseous silicon were studied, respectively. X-ray diffraction (XRD) reveals that the as-coated MWNTs are comprised of the amorphous SiC and the phase could transfer from amorphous to polycrystalline SiC by annealing at 1360 degrees C. Scanning electron microscopy (SEM) observation indicates that SiC nanoparticles are uniformly coated on the MWNTs, forming a continuous SiC coating. Thermogravimetric analysis (TGA) confirms that the onset temperature of oxidation increases from 540 to 700 degrees C with the SiC coating. The morphologies of non-coated and SiC-coated MWNTs after corrosion by oxygen and gaseous silicon were also characterized by SEM. The results revealed that SiC coating could protect MWNTs from the corrosion with gaseous silicon effectively.