Boron nitride nanotubes ( BNNTs) were synthesized by a carbon-free chemical vapor deposition method using boron and metal oxide as reactants. Then SnO2 nanoparticles were functionalized on them via a simple wet chemistry method. Detailed transmission electron microscopy (TEM) observations reveal that SnO2 nanoparticles may cover the tube surface or be encapsulated in tube channels. The lattice distances of both BNNT and SnO2 have been changed due to the strong interactions between them. The band gap energy of SnO2 particles is found enlarged due to the size effect and interaction with BNNTs.