This　investigation　focuses　on　the　design　of　functionalization　configuration　at　the　atomic　level　to　determine　the　influence　of　atomic　structure　on　the　mechanical　properties　of　functionalized　carbon　nanotubes　(F-CNTs)　and　their　composites.　Tension　and　compressive　buckling　behaviors　of　different　configurations　of　CNTs　functionalized　by　H　atoms　are　studied　by　a　molecular　dynamics　(MD)　method.　It　is　shown　that　H-atom　functionalization　reduces　Young＇s　modulus　of　CNTs,　but　Young＇smodulus　is　not　sensitive　to　the　functionalization　configuration.　The　configuration　does,　however,　affect　the　tensile　strength　and　critical　buckling　stress　of　CNTs.　Further,　the　stress-strain　relations　of　composites　reinforced　by　nonfunctionalized　and　various　functionalized　CNTs　are　analyzed.