Density functional molecular dynamics are used to study the melting behavior of single-walled SiC nanotubes. The melting of SiC nanotubes starts from the thermally activated Stone-Wales defects. The melting temperature is found to increase with the increasing diameter of nanotubes. The SiC nanotubes have a high melting temperature larger than 4000 K as the diameter larger than 1.0 nm, which indicates that the SiC nanotubes may be the best candidate of nanoscale electronic and optoelectronic devices under high temperatures.