The　cycloaddition　reactions　of　NH　to　different　bonds　on　C-70　have　been　studied　by　the　first-principles　calculations.　The　results　indicate　that　the　reactivity　of　cycloaddition　reactions　is　determined　by　the　directional　curvature,　K-D,　and　the　larger　binding　energy　of　E-b　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　C-5-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　C-5-C＇(5)　bond;　whereas,　the　addition　reaction　on　C-4-C＇(4)　is　a　spontaneous　pathway.　Herein,　the　dynamics　effect　illustrates　the　[2+1]　cycloaddition　reaction　on　the　equatorial　C-5-C＇(5)　bond　to　be　unfavorable.