The　cycloaddition　reactions　of　NH　to　different　bonds　on　C70　have　been　studied　by　the　first-principles　calculations.　The　results　indicate　that　the　reactivity　of　cycloaddition　reactions　is　determined　by　the　directional　curvature,　KD,　and　the　larger　binding　energy　of　Eb　on　the　bond　C　5-C＇5　can　be　ascribed　to　the　unique　bond　which　can　be　treated　as　the　shortest　bond　of　(5.5)-SWCNT　in　the　four　[6,6]　ring　fusion　bonds.　This　work　also　discloses　that　the　energy　gap　of　different　spin　states　is　decided　by　the　electronic　density,　and　that　of　the　frontier　obitals　for　the　bond　C5-C＇5　is　larger　than　the　value　for　the　C　4-C＇4　bond.　Furthermore,　the　transition　state　investigation　of　the　two　bond　addition　reactions　provides　a　reaction　barrier　of　11.10　kcal/mol　for　the　NH　cycloaddition　to　the　C5-C＇5　bond;　whereas,　the　addition　reaction　on　C4-C＇4　is　a　spontaneous　pathway.　Herein,　the　dynamics　effect　illustrates　the　[2+1]　cycloaddition　reaction　on　the　equatorial　C5-C＇5　bond　to　be　unfavorable.