TEX is a caged, nitramine type explosive material. To envisage the response of its bonds against stretching, an inert atom, helium, is doped into interior cavity of TEX molecule. Density functional theory at the level of B3LYP/6-31++G(d,p) was employed to investigate some physicochemical and quantum chemical properties of the helium-doped TEX (He@TEX) and compared with TEX and TEX+He composite systems. The result of helium doping caused swelling of TEX cage but no bond rupture occurred. The doped helium atom acquired positive charge.