Recent theoretical studies suggested that the stabilizing factors for large nitrogen cages tend to favor more five-membered rings, more three-membered rings and cylinder-shaped structure with large numbers of layers. Our present studies on the relative stability of all-nitrogen cages suggest that the stabilizing factors originate from the dispersion interactions. The cylinder-shaped of N66 (with D3h symmetry) has been studied in detail. The structure and energies are examined at the B3LYP/cc-pVDZ level. In addition, single-point energy calculations at the MP2/cc-pVDZ and the B3LYP/cc-pVTZ levels are carried out in order to determine whether or not dispersion interactions exist in N66. To fully understand the bonding in this cage molecule, NBO and AIM analyses are performed. The results show that the dispersion interactions contribute to the stability of the cylinder-shaped N66. Meanwhile, electrostatic potential analysis shows that N66 has negative electrostatic potential on the outside and positive electrostatic potential inside the tube. As the eleventh member of the series (N6)n (n = 1-30, with D3h or D3d symmetry alternatively), cylinder-shaped N66 may also be a novel beeline nanotube which is environmentally friendly. This work is expected to impact a wide range of applications.