The　adsorption　of　fluorine　and　hydrogen　on　the　armchair　(5,5)　single　wall　carbon　nanotubes　has　been　investigated　by　PM3　method.　The　nanotube　models　with　both　ends　open　contain　120C,　130C　and　140C,　respectively.　The　number　of　the　adsorbed　atoms　ranges　from　2　to　30.　It　is　shown　that　hydrogen　and　fluorine　have　similar　adsorbed　regularity,　but　the　adsorbed　stability　of　each　model　with　fluorine　was　much　more　different　from　that　with　hydrogen.　Under　50%　covering,　the　fluorine　atoms　tend　to　add　along　the　tube　axis　in　a　zigzag　form　instead　of　around　the　circumference　of　the　tubes,　corresponding　to　the　frontier　orbital　topological　diagram　of　each　model.