The　adsorption　and　reactivity　Of　O-2　on　perfect　and　defective　(10,　0)　boron　nitride　nanotubes　(BNNTs)　are　investigated　employing　the　density-functional　theory.　Our　results　indicate　that　O-2　prefers　to　physically　adsorb　on　perfect　BNNT.　The　assumed　dissociation　of　O-2　on　the　perfect　BNNT　is　endothermic　and　difficult　to　realize　with　an　energy　barrier　of　3.25　eV.　The　point　defects　such　as　vacancies　and　Stone-wales　defect　on.　the　wall　of　BN　nanotubes　reduce　the　oxidation　resistance　of　the　tubes.　Especially,　O-2　is　dissociated　on　nitrogen　vacancy　tube　with　a　barrier　of　0.84　eV.　The　electronic　properties　analysis　indicates　that　chemisorbed　O-2　can　reduce　the　energy-gap　of　BN　tubes.　(c)　2007　Elsevier　BN.　All　rights　reserved.