We report a simple, efficient method to in situ grow the Al₂O₃ coating on the surface of single-crystalline tubular SiC nanostructures with controllable morphology, size and population density. The nanostructures are fabricated by heating evaporation Al powders and C₆₀ on the Si substrates. By varying the reaction temperature, we can conveniently control the size and density of Al₂O₃ nanoparticles coating. Moreover, the ultrathin Al₂O₃ coating is also achieved by decreasing the quantity of Al source. The electrical transport measurement from single nanostructure is carried out to further confirm the excellent electrical insulation of ultrathin Al₂O₃ coating. This result contributes to the development of SiC based-nanodevices, as well as nanocomposites.