A　facile　and　general　method　was　described　to　coat　six　types　of　multi-walled　carbon　nanotubes,　functionalized　by　either　noncovalent　or　covalent　way,　with　smooth　silica　shells.　3-Aminopropyltriethoxysilane(APTES)　and　pH　value　play　important　roles　in　the　coating　process　and　the　thickness　of　silica　shell　could　be　controlled　by　the　added　amount　of　silicon　alkoxides.　After　the　removal　of　multi-walled　carbon　nanotubes　by　calcination,　the　silica　nanotubes　were　successfully　prepared.